NMSU: Thirty-five Years of Climatological Data: 1969-2003
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Authors: Respectively, College Associate Professor, Associate Professor, Research Technician, Research Specialist, College Associate Professor, all with the Agricultural Science Center at Farmington, New Mexico.

Plant growth and crop production are intrinsically linked to climate and daily weather conditions. Climate determines the types of plants that can be grown in a particular area and the management techniques required for successful landscapes and agricultural sustainability. Weather affects crop water requirements, timing of planting, cultivation, fertilization and harvest, crop tolerance to disease and pests, total crop yield and product quality. Agricultural and landscape planning begins with a thorough understanding of a locale's climate. To help provide this understanding for the Four Corners region, daily weather observations have been made since 1969 at the New Mexico State University (NMSU) Agricultural Science Center (ASC) at Farmington. The ASC is located in northwestern New Mexico (36° 4' N Lat., 108° 2' W Long.) about seven miles southwest of Farmington at an elevation of 5,640 feet above mean sea level. Two weather-data recording stations are located at the ASC. Station 1 (WS-1) was established at the center in January 1969 and was given an official designation by the National Weather Service (NWS) in 1978. Station 2 (WS-2) was installed approximately 400 yards south of WS-1 in 1985. This is an automated, computer-linked station that is operated and maintained by the New Mexico Climate Center (NMCC) at NMSU in Las Cruces. This report summarizes the weather observations from both of these stations between 1969 and 2003.

Summary

Compared to the mountainous areas that surround it, climate at the ASC is relatively dry and mild. Summer days are typically warm (90-95°F) and dry, while nights are cool (55-60°F). During the winter months of December and January, air temperatures commonly fall below 20°F in early morning, while daytime highs typically range between 35 and 45°F. The frost-free period averages 162 days from early May to mid-October, but crops such as potatoes, corn, spring cereals, etc. are usually planted before May 1. Throughout the year, days are typically clear and sunny. When precipitation events occur, they are usually of short duration and deposit less than 0.10 inch of rain per event. During the winter, snows are infrequent and snow depths greater than 6 inches are uncommon. Total annual precipitation averages 8.2 inches with about half of the total occurring in the so-called monsoon season (July-October). Twenty-four-hour rainfall amounts exceeding 1 inch have occurred less than 20 times during the entire 35 years of record. Some of the more extreme rainfall events were 1.5 inches on Oct. 22, 1969; 1.9 inches on Sept. 5-6, 1970; 2.7 inches on July 20-23, 1986; 1.9 inches on April 4-5, 1997; and 3.0 inches on Sept. 2-4, 2002. Compared to southern and eastern New Mexico, winds are relatively calm during the summer and winter, averaging about 110 miles per day (4.6 mph) between July and January. During March, April, and May, strong westerly winds are common and average wind velocity increases to about 150 miles per day (6.3 mph).

Materials and Methods

Weather Station 1

Air temperature measurements were recorded from standard U.S. Weather Bureau maximum and minimum thermometers housed in a regulation, louvered instrument shelter. A standard 8-inch diameter rain gauge was installed in 1969 to measure total daily precipitation. A battery-operated, constant-reading rain gauge was installed in 1982 to measure precipitation rate. Wind movement in miles per day has been recorded at two heights since 1980 using three-cup anemometers. One is located 6 inches above a standard Class-A metal evaporation pan, while the other is set at a height of 6 feet above the soil surface.

Water evaporation (pan) was measured daily from a Class-A pan with a hook-gauge from May 1 through September 30 in all years from 1974 to 2003. Pan measurements were also made throughout April in 1977 through 1981, 1986, and from 1992 through 2003. Complete October measurements were recorded in 1972, 1974 through 1978, 1984 and 1985, 1987 and 1988, 1990, and from 1992 through 2003.

Maximum and minimum bare-soil temperatures at a depth of 4 inches have been recorded since 1976, using buried temperature sensors. The soil type is a Doak fine sandy loam with about 70% sand, 20% silt, and 10% clay.

Using a pyranometer, daily solar radiation measurements were recorded from 1977 through 2003. Between January 1977 and September 1996, the instrument was set near the instrument shelter at a height of 6.5 feet. Subsequent readings were obtained at a 10-foot height from WS-2. Temperature and precipitation data recorded at WS-1 are summarized on the NWS Web site linked to: http://weather.nmsu.edu/nmcccooperator/farmington_ag_sci.htm.

Weather Station 2

The NMCC weather station consisted of air temperature, relative humidity, solar radiation, wind speed, wind direction, and rain-depth sensors wired to a Campbell CR10 datalogger. The datalogger, powered by a 12-volt, deep-cycle, lead-acid battery, and all sensors were mounted to a 3-meter high, steel and aluminum tripod. A solar-panel provided recharge to the battery. Measurements were recorded to the datalogger every 15 minutes, and the data were downloaded to a PC at the NMCC via modem and telephone line. WS-2 data are accessible from the NMCC Web site: http://weather.nmsu.edu/cgi-shl/cns/oldformat.pl.

Unless noted otherwise, data presented in this report are from WS-1.

Results

Air Temperature

Between 1969 and 2003, the daily minimum, mean, and maximum air temperatures averaged over all months and years were 38.7, 52.6, and 66.4°F, respectively (fig. 1, tables 1, 2, and 3). Average annual minimums ranged from 36.1°F in 1975 to 40.8°F in 2001 (table 1), while average maximums ranged from 63.7°F in 1982 to 69.3°F in 2003 (table 3). The highest annual mean temperature of 55.1°F during the 35-year period occurred in 2003 (table 2). This was primarily due to record or near record high average minimum (64, 62, and 44°F) and maximum (97, 91, and 74°F) temperatures for July, August, and October, respectively (tables 1 and 3). The coolest year on record (1975) appeared to be a result of lower than average minimum temperatures in May and June (table 1).

Fig. 1: Line graph of average daily minimum, mean, and maximum air temperature for each year, 1969-2003. FIG-1.tif

Figure 1. Average daily minimum, mean, and maximum air temperature for each year at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Table 1. Average daily minimum temperature (°F) for each month at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Mean
1969 25 24 24* 35 48** 51 61 62** 55 39 30 22 39.7
1970 20 27 26 29* 43 53 62 62** 49 36 30 22 38.3
1971 16 20 26 33 42 54 61 60 48 38 28 21 37.3
1972 18 22 31 36 43 55 62 60 53 45** 27 15 38.9
1973 12* 26 29 32 44 52 60 60 48 40 31 19 37.8
1974 14 17* 33 33 46 57 61 59 50 44 28 17 38.3
1975 14 23 28 31 40* 48* 60 57 50 39 24 19 36.1*
1976 16 28 25 36 45 53 62 59 54 37 26 17 38.2
1977 15 22 25 39 44 59** 62 61 55 42 31 26** 40.1
1978 25 25 33 38 43 53 61 57 52 43 33** 15 39.8
1979 16 22 28 34 44 50 58 57 53 40 25 20 37.3
1980 26** 28 27 33 41 52 59 58 50 35* 27 24 38.3
1981 20 23 29 39 44 54 58 56* 50 37 30 22 38.5
1982 18 21 30 34 43 51 58 60 52 35* 29 22 37.8
1983 21 26 31 31 41 51 58 61 52 41 29 24 38.8
1984 16 20 27 33 48** 53 61 60 52 36 30 25 38.4
1985 20 19 32 38 46 54 61 59 48 41 29 19 38.8
1986 23 26 33 39 44 55 59 60 50 40 29 22 39.8
1987 18 25 26 39 45 53 57* 57 49 40 28 19 37.0
1988 13 24 25 36 44 56 61 60 48 43 29 19 38.2
1989 16 24 34 40 47 54 63 58 54 40 26 16 39.3
1990 18 25 35** 41** 45 59** 63 60 56** 40 30 11* 40.2
1991 16 25 30 34 44 53 59 59 51 40 27 21 38.3
1992 18 27 32 40 48** 52 57* 58 50 40 22* 16 38.4
1993 26** 28 30 36 45 52 57* 58 48 38 25 20 38.4
1994 19 24 31 38 46 56 60 61 50 39 27 24 39.6
1995 24 29** 31 35 43 50 58 61 52 37 29 23 39.3
1996 19 28 29 34 47 54 60 58 47 38 28 21 38.6
1997 19 24 28 32 46 54 59 59 54 37 28 20 38.2
1998 22 25 28 33 45 48* 62 59 54 40 29 19 38.5
1999 21 24 31 34 43 50 59 57 46* 36 28 15 37.0
2000 22 28 29 37 44 54 58 58 52 42 25 23 39.3
2001 21 26 32 40 47 54 63 59 54 42 32 19 40.8**
2002 19 18 26 41** 46 57 61 58 51 39 27 22 38.8
2003 25 24 31 35 47 53 64** 62** 50 44 29 22 40.5
Mean 19.2 24.2 29.3 35.7 44.6 53.3 60.1 59.1 51.1 39.5 28.1 20.0 38.7
*Lowest average daily minimum temperature for month or year during 35-year period.
** Highest average daily minimum temperature for month or year during 35-year period.

Table 2. Average daily mean temperature (°F) in each month at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Mean
1969 34 35 37* 52 63 67 76 76 69 50 40 34 52.8
1970 31 40 39 44* 60 68 76 76 64 50 42 33 51.9
1971 30 34 43 50 58 71 77 74 64 52 40 30 51.9
1972 30 38 48 53 60 70 78 74 66 54 36 26 52.8
1973 22* 35 39 45 59 68 75 75 63 55 44 30 50.8
1974 24 28* 48 48 63 74 75 74 65 55 40 28 51.8
1975 26 34 40 46 56* 66* 74 72 64 54 38 30 50.0*
1976 28 41 40 52 60 70 77 74 66 51 40 32 52.6
1977 25 37 39 54 59 74 76 75 68 56 43 36 53.5
1978 33 34 46 52 56* 69 76 71* 65 56 42 24* 52.0
1979 24 32 40 50 58 67 74 72 69 56 35* 32 50.8
1980 33 39 40 48 57 71 76 73 65 52 41 37** 52.7
1981 30 37 41 55 59 71 74 72 65 51 44 34 52.8
1982 30 31 42 49 57 67 73 72 65 50 40 32 50.7
1983 31 36 42 45 56* 66* 74 75 68 54 41 34 51.8
1984 28 34 41 47 64** 69 76 74 66 47* 42 35 51.9
1985 30 32 41 53 61 71 76 74 62 54 40 31 52.1
1986 40** 39 47 51 60 70 72* 74 62 52 40 33 53.3
1987 29 36 39 53 59 70 73 71* 65 56 39 29 51.6
1988 24 36 41 51 59 72 76 74 64 58 41 31 52.3
1989 27 35 49** 57** 63 70 78 72 69 55 41 31 53.9
1990 29 36 46 54 59 75** 76 73 69 54 42 24* 53.1
1991 25 37 41 49 59 68 75 74 66 56 38 29 51.4
1992 28 39 45 56 62 68 72* 73 66 56 35* 26 52.2
1993 35 38 44 51 61 69 74 71* 64 52 38 32 52.4
1994 33 35 46 52 61 73 77 76 66 53 38 35 53.8
1995 33 44** 44 48 57 67 74 76 67 53 44 35 53.5
1996 32 41 43 51 64** 71 76 73 61* 52 40 32 53.0
1997 29 36 46 47 61 70 74 73 68 52 41 31 52.3
1998 34 35 42 48 61 67 77 74 70** 54 42 32 53.0
1999 35 39 48 49 58 68 74 71* 63 54 45** 30 52.8
2000 34 40 42 53 63 71 75 75 68 54 35* 34 53.7
2001 31 37 45 54 63 71 77 74 70** 57 45** 31 54.6
2002 32 34 42 57** 63 75** 78 74 66 53 40 32 53.8
2003 38 36 44 51 63 71 81** 77** 66 59** 41 34 55.1**
Mean 30.2 36.3 42.9 50.7 60.1 69.9 75.5 73.7 65.8 53.6 40.4 32.0 52.6
* Lowest average daily mean temperature for month or year during 35-year period.
** Highest average daily mean temperature for month or year during 35-year period.

Table 3. Average daily maximum temperature (°F) in each month at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Mean
1969 42 46 50* 69 78 81* 91 90 83 62 51 45 65.7
1970 42 54 52 60 78 84 91 91** 78 63 55 44 66.0
1971 43 48 59 66 74 87 93 87 80 65 51 39 66.0
1972 43 54 66** 70 78 86 93 87 80 63 46* 37 66.9
1973 32 42 50* 59* 74 84 90 90 79 70 57 42 64.1
1974 34 40* 62 64 80 91 89 88 80 66 52 39 65.4
1975 37 44 52 60 71 85 89 88 79 70 53 42 64.2
1976 41 54 56 68 76 87 92 88 79 65 53 45 67.0
1977 34 51 53 69 74 90 90 89 81 71 54 47 66.9
1978 41 44 58 65 70* 85 90 86 78 70 51 33* 64.3
1979 31* 42 52 65 72 84 90 86 84 71 46* 43 63.8
1980 41 50 53 64 72 89 93 88 80 66 55 51** 66.8
1981 49 51 53 70 74 88 90 88 80 65 58 46 67.7
1982 41 41 54 63 72 84 89 85 78 65 51 41 63.7*
1983 40 46 53 59* 72 82 90 89 83 68 52 43 64.8
1984 41 48 56 61 80 84 91 87 80 60* 55 45 65.7
1985 41 44 55 67 75 88 91 89 76 67 51 43 65.6
1986 49 51 61 64 75 84 86* 89 75* 65 50 44 66.1
1987 40 47 52 68 74 87 90 86 80 71 51 40 65.5
1988 35 47 57 65 75 87 92 87 80 73 53 43 66.2
1989 38 45 63 73** 79 86 93 87 84 69 56 45 68.2
1990 41 47 58 67 73 90 90 87 82 68 54 36 66.1
1991 35 49 53 65 75 84 90 88 80 71 49 37 64.7
1992 38 50 58 71 76 84 86* 87 81 72 48 36 65.6
1993 44 48 59 67 76 86 91 85 79 66 50 43 66.2
1994 46 46 61 66 76 90 93 91** 81 66 50 46 67.7
1995 42 58** 58 61 71 83 91 90 81 69 59 47 67.5
1996 45 54 58 68 82** 87 91 89 76 66 53 43 67.7
1997 39 48 63 61 77 86 90 87 82 67 54 42 66.3
1998 45 46 57 62 78 85 92 90 86** 68 56 45 67.5
1999 50 54 64 63 73 86 89 84* 80 73 63** 44 68.6
2000 47 53 56 68 82** 89 93 91** 84 66 46* 45 68.3
2001 41 48 57 68 79 89 92 88 85 72 59 43 68.4
2002 45 49 57 72 79 93** 94 90 80 66 53 43 68.4
2003 51** 48 56 67 79 88 97** 91** 82 74** 52 46 69.3**
Mean 41.3 48.2 56.6 65.6 75.7 86.4 90.9 88.1 80.5 67.7 52.8 42.7 66.4
* Lowest average daily maximum temperature for month or year during 35-year period.
** Highest average daily maximum temperature for month or year during 35-year period.

January and December were the coldest months, having average daily minimum, mean, and maximum temperatures of about 20, 31, and 42°F, respectively (fig. 2). July and August had the highest average daily temperatures (60°F minimum, 75°F mean, and 90°F maximum).

Fig. 2: Bar graph of average daily minimum, mean, and maximum air temperature for each month, 1969-2003.

Figure 2. Average daily minimum, mean, and maximum air temperature for each month at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Frost-Free Period

The frost-free period (consecutive days above 32°F) averaged 162 days over the 35 years (table 4). The shortest frost-free period occurred in 1999 (115 days), the only year in which a June frost was recorded. The longest frost-free period occurred in 1977 (193 days). The average dates of the last spring frost and first autumn frost were May 5 and Oct. 13, respectively. The earliest and latest dates of the last spring frost were April 10, 1990 and June 5, 1999, respectively. The earliest and latest dates of the first fall frost were Sept. 18, 1971 and Nov. 12, 1988 (table 4). The number of consecutive days without a killing frost (28°F or less) averaged 182. A killing frost results in substantial damage to most plants. A temperature of 28°F for more than 30 minutes, for example, will kill approximately 10% of apple or cherry blossoms during flowering (Longstroth, 2001).

Table 4. Frost dates and number of consecutive frost-free days at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year ---------- Less than or equal to 32°F ------------ --------------- Less than or equal to 28°F ----------------
Last Spring Frost (date) First Fall Frost (date) Frost-Free Period (days) Last Spring Killing Frost (date) First Fall Killing Frost (date) Killing Frost- free-period (days)
1969 April 27 Oct. 5 161 April 26 Oct. 6 163
1970 May 2 Oct. 8 159 May 1 Oct. 9 161
1971 May 9 Sept. 18* 132 April 27 Sept. 18* 144*
1972 May 2 Oct. 30 181 April 27 Oct. 31 187
1973 May 2 Oct. 11 162 May 2 Oct. 27 178
1974 May 21 Oct. 30 162 May 20 Nov. 4 168
1975 May 8 Oct. 14 159 May 7 Oct. 14 160
1976 April 27 Oct. 7 164 April 27 Oct. 19 175
1977 April 21 Oct. 31 193** April 5 Nov. 2 211
1978 May 6 Oct. 26 173 May 6 Nov. 13 191
1979 May 12 Oct. 21 162 April 20 Oct. 22 185
1980 May 26 Oct. 16 143 May 25** Oct. 17 145
1981 May 9 Oct. 16 160 April 5 Oct. 17 194
1982 May 6 Oct. 6 153 April 21 Oct. 10 172
1983 May 19 Sept. 21 125 May 17 Nov. 9 176
1984 May 8 Oct. 15 160 May 8 Oct. 16 161
1985 May 14 Sept. 30 139 April 1 Nov. 1 214
1986 April 27 Oct. 12 168 April 27 Oct. 13 169
1987 April 21 Oct. 19 181 April 21 Nov. 11 204
1988 May 7 Nov. 12** 189 April1 1 Nov. 16** 219**
1989 April 30 Oct. 18 171 March 21 Oct. 27 219**
1990 April 10* Oct. 9 181 March 31 Oct. 21 204
1991 May 5 Oct. 28 176 March 29 Oct. 29 214
1992 April 21 Oct. 8 170 March 19* Oct. 8 203
1993 May 9 Oct. 19 163 April 20 Oct. 27 190
1994 April 30 Oct. 17 170 April 8 Oct. 31 206
1995 April 25 Oct. 6 164 April 18 Oct. 6 171
1996 April 30 Sept. 19 142 April 29 Oct. 18 172
1997 May 2 Oct. 13 163 May 2 Oct. 13 163
1998 May 15 Oct. 6 144 April 19 Oct. 6 170
1999 June 5** Sept. 28 115* April 16 Sept. 29 166
2000 May 12 Oct. 14 154 April 3 Nov. 2 212
2001 April 23 Oct. 11 170 April 13 Oct. 11 180
2002 April 22 Oct. 4 165 April 22 Nov. 4 196
2003 May 11 Oct. 27 168 April 8 Oct. 27 201
Mean May 5 Oct. 13 162 April 21 Oct. 22 182
*Earliest date (or shortest frost-free period).
**Latest date (or longest frost-free period

Extreme Temperatures

Although the average number of days between the first autumn frost and last spring frost was 204, the temperature dropped below 32°F on only 139 of those days (table 5). In the months of November through March, the temperature dropped below freezing about 25 days per month on average (table 5). The temperature dropped to zero or below 1.8 days per year on average between 1969 and 1992 but fell below zero only once since 1992 (table 5). The coldest temperatures recorded during the 35-year period were -18°F, -16°F, and -14°F and occurred in January 1971, December 1990, and February 1989, respectively (table 6).

Table 5. Number of days 32°F or below and 0°F or below in the winter, spring, and fall months at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year ------------------------ Number of Days 32°F or Below ------------------- --- Number of Days 0°F and Below ---
Jan. Feb. Mar. Apr. May Sept. Oct. Nov. Dec. Total Jan. Feb. Dec. Total
1969 22 26 25 7 0 0 7 22 29 138 0 0 0 0
1970 29 25 26 23 2 0 12 23 30 170 1 0 0 1
1971 29 27 22 13 1 2 8 26 27 155 4 0 0 4
1972 31 27 19 10 2 0 2 24 31 146 0 0 0 0
1973 31 26 25 17 1 0 5 16 28 149 0 0 0 0
1974 30 28 14 14 2 0 2 24 30 144 2 0 0 2
1975 29 27 24 15 3 0 6 25 30 159 2 0 0 2
1976 31 22 24 8 0 0 10 22 31 148 2 0 0 2
1977 31 28 26 8 0 0 1 20 30 144 3 0 0 3
1978 28 21 12 6 2 0 1 14 29 113 0 1 5 6
1979 29 27 25 11 3 0 5 24 31 155 3 1 0 4
1980 23 21 25 15 2 0 12 18 28 144 0 0 0 0
1981 29 26 24 3 1 0 11 19 31 144 0 0 0 0
1982 29 25 18 12 1 0 12 22 29 148 1 2 0 3
1983 31 25 18 15 6 1 0 18 26 140 0 0 0 0
1984 31 29 24 15 1 0 12 18 29 159 0 0 0 0
1985 31 25 16 5 1 1 2 19 30 130 0 1 0 1
1986 28 21 20 6 0 0 6 18 29 128 0 0 0 0
1987 28 25 24 10 0 0 3 22 31 143 0 0 0 0
1988 31 25 27 9 2 0 0 16 29 139 2 0 0 2
1989 31 24 13 5 0 0 6 27 31 137 0 2 0 2
1990 30 21 14 3 0 0 6 19 28 121 2 0 7 9
1991 31 22 20 11 2 0 4 23 31 144 2 0 0 2
1992 31 23 15 3 0 0 2 28 29 131 0 0 1 1
1993 28 22 24 11 3 0 9 25 31 153 0 0 0 0
1994 30 24 14 8 0 0 4 22 28 130 0 0 0 0
1995 28 18 15 15 0 0 7 23 28 134 0 0 0 0
1996 31 23 21 11 0 2 9 24 28 149 0 0 0 0
1997 29 27 23 16 1 0 11 22 31 160 1 0 0 1
1998 31 23 20 17 1 0 4 22 30 148 0 0 0 0
1999 30 26 19 12 4 2 8 24 30 156 0 0 0 0
2000 25 23 24 5 1 0 1 24 29 132 0 0 0 0
2001 31 23 13 6 0 0 2 13 29 117 0 0 0 0
2002 31 28 23 2 0 0 4 25 31 144 0 0 0 0
2003 30 22 21 9 3 0 2 18 29 134 0 0 0 0
Mean 29.4 24.0 20.0 10.0 1.3 0.2 5.9 21.0 29.5 139 1 0.2 0.4 1.3

Table 6. Lowest temperatures (°F) recorded in each month at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
1969 9 12 13 27 37 44 43* 52 46 26 14 7
1970 0 15 11 20 27 39 53 54 34 21 18 14
1971 -18* 5 6 17 31 38 54 54 28* 18 17 4
1972 2 2 14 24 30 47 56 54 37 22 15 2
1973 1 10 20 18 28 41 52 49 37 26 14 9
1974 -11 1 20 18 28 38 53 52 33 30 14 1
1975 -2 9 9 19 23* 38 55 49 40 20 7 6
1976 -4 12 11 23 34 38 54 52 42 22 1* 9
1977 -2 13 12 21 33 51 57 54 46 32 20 10
1978 12 0 20 26 31 45 51 46 32 31 18 -9
1979 -8 5 17 16* 29 36 51 51 42 23 6 9
1980 14 18 13 18 27 36 53 41* 37 17 12 11
1981 10 11 21 19 32 36 44 49 42 21 13 4
1982 -1 -3 19 22 30 38 47 54 38 21 17 6
1983 9 20 22 20 27 36 61 55 30 35 11 10
1984 2 11 14 18 27 40 53 54 39 23 15 13
1985 6 -1 13 28 29 39 53 51 31 31 8 8
1986 8 8 19 23 33 42 53 52 40 28 16 8
1987 2 8 9 24 35 43 50 47 40 32 14 1
1988 -2 16 9 21 30 38 54 54 33 36 12 1
1989 4 -14* 14 29 36 41 55 48 36 15* 9 3
1990 0 4 19 30 39 47 55 52 45 26 16 -16*
1991 -3 12 17 24 30 39 53 54 39 20 11 3
1992 10 17 20 30 40 41 47 48 37 28 7 -2
1993 10 18 18 24 32 39 49 52 38 17 8 8
1994 7 4 12 26 35 46 50 57 39 26 8 11
1995 12 21 18 24 34 38 45 55 36 24 13 9
1996 6 12 16 20 39 41 54 52 29 16 19 3
1997 -1 13 13 19 26 46 51 53 43 19 17 8
1998 12 15 13 25 31 40 59 52 46 27 16 3
1999 11 7 21 20 30 32* 50 49 28* 19 9 3
2000 1 14 17 28 29 44 52 52 33 32 10 11
2001 10 8 21 24 34 36 57 52 36 28 13 8
2002 3 6 3* 27 35 48 56 50 39 30 19 8
2003 17 8 22 24 29 46 53 57 41 28 12 7
*Lowest recorded monthly temperature.

The temperature exceeded 95°F about 13 days per year on average and, while it exceeded 100°F on only 28 days of the entire 35-year period, nine of the 28 days occurred in July 2003. The highest recorded temperature of 103°F occurred in July 1989, 1990, and 2003 (table 7).

Table 7. Highest temperatures (°F) recorded in each month at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
1969 57 61 74 82 89 96 96 99* 95 78 63 56
1970 56 65 65 72 86 98 98 99* 90 76 64 61
1971 60 64 77 77 84 97 101 91 90 67 70 57
1972 61 66 76 78 86 94 100 98 89 82 57 52
1973 47 61 63 76 85 98 99 97 88 81 73 65
1974 45 60 72 75 93 99 95 94 93 83 64 56
1975 61 58 65 77 85 96 95 95 89 84 73 57
1976 54 68 71 77 86 96 100 93 94 78 70 55
1977 46 65 69 81 91 98 97 98 93 82 74 63
1978 53 59 79 77 88 95 95 94 90 83 67 47
1979 46 60 62 78 82 96 97 96 94 83 60 54
1980 55 64 67 81 86 99 97 97 88 84 73 63
1981 60 67 71 82 84 100* 97 96 85 78 68 56
1982 60 64 64 75 75 93 97 95 91 79 64 53
1983 53 68 68 83 89 92 96 99* 93 74 70 50
1984 51 60 68 79 93 94 95 93 89 75 68 54
1985 50 60 70 79 85 95 100 95 93 75 68 51
1986 64 70* 75 79 85 94 96 96 88 75 63 55
1987 56 61 69 80 82 93 98 93 89 83 66 58
1988 49 62 77 78 87 99 96 93 93 83 70 56
1989 50 67 81* 85 90 98 103* 92 91 85 67 53
1990 56 64 74 80 86 100* 103* 94 93 79 69 55
1991 44 58 67 79 85 94 97 93 91 82 67 46
1992 52 58 67 86* 85 92 95 95 89 83 61 49
1993 54 61 72 81 86 96 96 96 88 84 61 56
1994 58 63 74 81 90 100* 98 97 89 80 70 55
1995 53 68 74 77 82 92 101 97 97* 83 68 64
1996 56 65 71 82 90 93 96 96 90 83 66 57
1997 58 60 75 76 88 93 98 92 91 84 68 54
1998 56 62 77 80 87 99 100 95 90 85 67 60
1999 62 65 75 78 85 94 99 91 89 85 75* 67*
2000 66* 66 70 85 97* 94 97 97 93 83 57 55
2001 51 62 70 81 90 96 99 94 93 86 75* 59
2002 59 63 74 81 95 98 100 99* 90 77 63 55
2003 57 59 74 78 95 96 103* 98 92 87* 67 62
*Highest recorded monthly temperature.

Precipitation

From 1969 through 2003, the average annual precipitation was 8.16 inches (fig. 3 and table 8). Annual precipitation extremes ranged from a low of 3.57 inches in 1976 to a high of 14.65 inches in 1986 (fig. 3). The average monthly precipitation ranged from a low of 0.26 inches in June to 1.10 inches in August (fig. 4). The greatest amount of rainfall in a single month was 4.10 inches in July 1986. In 22 months over the 35 years, there was no measurable precipitation (table 8).

Fig. 3: Bar graph of total annual precipitation, 1969-2003.

Figure 3. Total annual precipitation measured at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Table 8. Total monthly precipitation depth (inches) recorded at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Total
1969 0.85 0.31 0.21 0.30 1.13 1.00* 0.69 0.47 2.07 2.88 0.38 0.29 10.58
1970 0.06 0.03 0.49 0.60 0.11 0.81 0.68 0.02 2.48 0.48 0.46 0.20 6.42
1971 0.18 0.09 0.05 0.11 0.41 0.00 0.31 1.72 1.06 1.15 0.77 0.16 6.01
1972 0.03 T 0.03 0.00 0.02 0.18 0.04 1.34 0.57 3.53* 0.19 0.93 6.86
1973 0.28 0.17 1.82 1.54 0.65 0.95 0.27 0.61 1.49 0.35 0.30 0.37 8.80
1974 1.10 0.13 0.01 0.20 0.02 0.09 1.48 0.12 0.37 2.39 0.48 0.38 6.77
1975 0.11 0.61 1.52 0.78 0.35 0.13 0.84 0.24 0.80 0.14 0.22 0.20 5.94
1976 0.06 0.16 0.00 0.10 0.41 0.09 0.62 0.80 1.31 0.01 0.01 T 3.57**
1977 0.42 T 0.00 0.01 0.29 0.04 1.01 1.41 0.38 0.30 0.62 0.63 5.11
1978 0.90 0.64 1.27 0.71 0.96 0.00 0.07 0.18 1.55 1.46 2.24 0.59 10.57
1979 0.88 0.19 0.46 0.28 0.58 0.43 1.40 0.49 0.08 1.37 0.97 0.73 7.86
1980 1.45 0.70 0.63 0.25 0.25 0.07 0.08 0.89 1.05 0.84 0.02 T 6.23
1981 T 0.30 1.76 0.21 1.05 0.16 1.34 0.35 0.69 0.89 0.36 0.03 7.14
1982 0.32 0.77 1.18 0.67 0.82 0.00 1.27 2.78 1.50 0.16 0.92 0.76 11.15
1983 0.94 0.69 1.84 0.31 0.13 0.35 1.67 0.72 0.53 0.52 0.91 0.67 9.28
1984 T 0.12 0.54 1.00 T 0.67 0.62 1.64 0.45 1.13 0.23 0.87 7.27
1985 0.39 0.13 1.74 1.76 0.29 0.01 1.38 0.43 1.31 1.21 0.52 0.22 9.39
1986 0.11 0.77 0.51 0.97 0.13 0.81 4.10* 0.93 2.18 0.65 2.73* 0.76 14.65*
1987 0.10 1.75* 0.66 T 0.68 0.02 0.28 1.17 0.27 1.07 1.65 0.59 8.24
1988 0.63 0.82 0.02 0.72 1.11 0.33 0.58 2.34 0.27 0.22 0.78 0.19 8.01
1989 1.19 0.56 0.06 0 T T 1.24 1.62 0.14 0.51 0.00 T 5.32
1990 0.53 0.53 0.74 0.85 1.07 0.07 0.35 1.32 1.97 1.12 0.78 0.59 9.92
1991 0.59 0.26 0.67 0.01 0.27 0.69 0.35 0.58 1.38 0.38 2.07 1.01* 8.26
1992 0.15 0.18 0.74 0.25 1.75* 0.05 0.98 1.25 0.85 0.42 0.31 0.63 7.56
1993 2.05* 0.82 0.93 0.28 0.38 0.04 0.03 2.06 0.84 1.25 0.47 0.15 9.30
1994 0.09 0.48 0.24 0.57 1.32 0.07 0.20 0.66 1.37 1.18 0.96 0.64 7.78
1995 0.57 0.14 1.45 1.28 0.90 0.03 0.23 1.88 2.04 0.10 0.14 0.39 9.15
1996 0.09 0.43 0.28 0.17 0.00 0.64 0.24 1.07 0.63 2.21 0.72 0.22 6.70
1997 1.03 0.48 0.03 2.88* 0.82 0.62 1.28 1.12 2.68 0.43 0.67 0.80 12.84
1998 0.12 0.61 0.65 0.73 0.03 0.02 1.38 1.48 0.68 2.07 1.27 0.06 9.10
1999 0.14 0.05 0.13 1.21 1.26 0.44 2.51 2.99* 0.25 0.01 0.06 0.12 9.17
2000 0.62 0.25 2.05* 0.21 0.03 0.12 0.80 1.22 0.50 2.16 0.78 0.22 8.96
2001 0.44 0.80 1.37 0.67 0.87 0.03 0.82 1.01 0.26 0.24 0.48 0.55 7.54
2002 0.04 0.04 0.17 0.37 0.00 0.00 0.42 0.32 3.26* 1.75 0.72 0.60 7.69
2003 0.08 1.29 0.49 0.02 0.01 0.15 0.11 1.24 0.87 0.72 1.03 0.31 6.32
Mean 0.47 0.44 0.71 0.57 0.52 0.26 0.85 1.10 1.09 1.01 0.72 0.42 8.16
*Highest recorded precipitation for month (or year) in 35-year period.
**Lowest recorded precipitation for year in 35-year period.
T - Trace

Fig. 4: Bar graph of average monthly precipitation, 1969-2003.

Figure 4. Average monthly precipitation measured at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Wind

Since 1980, the average daily wind run at the 6-foot height has been 123.4 miles/day (5.1 mph). But it varied considerably between the spring months and rest of the year (fig. 5 and table 9). March and April were the windiest months, with an average daily wind run at the 6-foot height of more than 150 miles/day. The calmest months of August through December had an average daily wind run of about 110 miles (fig. 5). In 1991, March and April were particularly windy with an average daily wind run at the 6-foot height of 190 miles (table 9).

Fig. 5: Bar graph of average daily wind run at a height of 6 feet for each month, 1969-2003.

Figure 5. Average daily wind run at a height of 6 feet for each month at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Table 9. Average daily wind run (miles/day) measured at two heights (2 feet and 6 feet) during each month at NMSU's Agricultural Science Center at Farmington, 1980-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Mean
------------------------------------- 2 feet (6 inches above evaporation pan) ----------------------------------------
1980 64 66 100 97 80 57 44 41 27 30 23 14 53.6
1981 50 80 94 85 71 64 58 60 20 55 56 52 62.1
1982 69 36 63 89 78 42 59 75 77 86 77 89 70.0
1983 82 101 107 101 108 98 76 70 62 73 94 98 89.2
1984 63 101 104 114 78 94 66 61 70 71 99 67 82.3
1985 49 87 128 98 76 66 70 76 70 72 148 55 82.9
1986 53 61 72 95 78 64 52 66 60 45 50 45 61.8
1987 60 41 50 50 31 22 25 19 21 48 71 79 43.1
1988 76 73 99 88 99 81 75 71 75 64 82 82 80.4
1989 84 75 96 86 69 73 78 72 73 68 68 59 75.1
1990 78 97 90 91 91 84 82 82 76 72 71 83 83.1
1991 61 73 106 98 99 75 79 67 72 57 59 47 74.4
1992 64 66 80 76 72 74 66 70 62 58 68 66 68.5
1993 103 86 105 107 91 81 71 75 74 65 82 79 84.9
1994 81 96 83 94 71 61 72 72 63 58 84 59 74.5
1995 76 65 83 81 80 61 63 59 52 64 58 49 65.9
1996 92 79 88 93 72 73 72 60 44 51 53 71 70.7
1997 43 79 78 73 70 62 55 48 50 48 39 35 56.8
1998 59 75 83 81 66 72 70 66 62 78 66 59 69.5
1999 76 74 83 109 95 70 63 63 61 65 73 78 75.8
2000 83 88 93 93 85 80 66 64 62 63 60 57 74.5
2001 65 74 72 91 83 77 64 67 74 74 65 75 73.4
2002 74 90 104 83 59 64 69 55 62 50 56 49 67.9
2003 36 58 60 68 70 70 56 60 56 50 56 62 58.5
Mean 68.4 75.9 88.4 89.2 78.0 69.4 64.6 63.3 59.4 61.0 69.1 62.9 70.8
  -------------------------------------------------- 6 feet above ground --------------------------------------------------
1980 --- --- --- --- 134 132 116 96 82 78 80 84 ---
1981 112 124 141 124 102 81 62 82 71 81 76 58 92.8
1982 88 63 97 127 100 122 103 91 99 95 86 99 97.5
1983 111 139 147 154 141 120 116 102 113 107 130 136 126.3
1984 64 115 93 136 88 96 52 46 49 44 136 110 85.7
1985 95 127 183 155 142 136 136 133 125 127 72 117 129.0
1986 113 129 145 179 154 139 128 134 128 118 116 99 131.9
1987 139 131 143 158 139 126 122 119 132 108 123 117 129.7
1988 121 122 163 148 166 138 132 126 120 91 98 98 126.8
1989 97 133 151 147 132 123 126 120 125 115 112 104 123.8
1990 125 152 146 170 165 154 141 136 127 135 127 130 142.2
1991 101 120 190 191 167 138 140 119 129 111 109 85 133.4
1992 117 119 137 142 133 137 118 118 111 110 113 106 121.6
1993 164 139 153 171 144 86 57 80 103 87 92 --- ---
1994 130 156 144 166 135 130 136 127 120 119 154 115 136.0
1995 137 129 147 176 185 137 128 118 115 137 129 100 136.5
1996 171 145 161 182 149 140 127 119 112 134 119 147 142.3
1997 106 149 146 153 137 113 112 101 105 115 118 110 122.1
1998 100 133 145 144 112 120 111 100 105 131 111 106 118.2
1999 143 142 145 186 196 92 85 100 107 98 93 126 126.1
2000 132 141 149 158 144 135 108 104 108 110 113 109 125.9
2001 116 127 173 147 141 128 106 108 121 125 110 132 127.8
2002 117 144 163 134 126 115 114 96 108 90 110 107 118.7
2003 98 134 143 139 134 128 106 107 113 103 116 129 120.8
Mean 117.3 131.0 148.0 156.0 140.3 123.6 111.8 107.6 109.5 107.0 110.1 109.7 123.4

Solar Radiation

From 1977 to 2003, average daily solar radiation, measured as gram calories/cm2 (Langley's), ranged from a low of about 200/day in January and December to a high of about 625/day in June and July (fig. 6 and table 10). Total annual radiation averaged about 154,000 Langley's (421 Langley's/day).

Fig. 6: Bar graph of average daily solar radiation for each month, 1977-2003.

Figure 6. Average daily solar radiation for each month at NMSU's Agricultural Science Center at Farmington, 1977-2003.

Table 10. Average daily solar radiation (gram cal/cm2 or Langleys) at NMSU's Agricultural Science Center at Farmington, 1977-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Mean
1977 204 305 386 552 438 530 501 464 396 360 --- --- 413.6
1978 157 168 334 459 490 586 641 491 401 292 185 166 364.2
1979 166 261 302 423 445 527 489 477 459 267 165 155 344.7
1980 141 192 300 429 459 529 595 501 436 342 280 145 362.4
1981 190 296 292 473 499 607 550 489 422 314 248 200 381.7
1982 129 207 369 536 594 707 651 565 470 393 227 208 421.3
1983 188 294 345 518 654 734 793 725 583 332 230 176 464.3
1984 250 345 486 540 688 494 736 744 595 317 226 188 467.4
1985 242 303 359 499 561 648 590 561 413 335 228 214 412.8
1986 243 304 410 468 586 573 549 509 352 313 215 205 393.9
1987 229 289 411 566 551 665 638 542 483 352 246 197 430.8
1988 220 305 474 496 626 623 621 555 486 470 251 216 445.3
1989 224 280 419 550 628 633 619 570 498 361 277 219 439.8
1990 222 282 316 479 593 662 620 541 462 361 234 203 414.6
1991 212 309 356 554 651 556 613 537 450 340 249 146 414.4
1992 189 268 358 509 530 616 560 501 451 324 238 167 392.6
1993 160 230 374 514 532 599 614 464 456 331 240 187 391.8
1994 223 262 371 439 482 564 555 496 411 300 225 178 375.5
1995 189 288 358 438 481 552 520 459 373 324 212 157 362.6
1996 240 309 463 580 651 609 676 604 458 357 250 226 451.9
1997 215 314 516 513 613 657 640 567 491 390 267 220 450.3
1998 236 260 443 563 661 725 604 565 506 331 266 244 450.3
1999 263 363 458 527 624 702 584 515 505 438 320 241 461.7
2000 251 305 399 581 689 696 673 579 479 325 255 213 453.8
2001 241 322 424 508 672 766 633 580 541 396 286 248 468.1
2002 251 383 492 593 710 742 663 601 479 372 294 219 483.3
2003 249 315 452 596 640 719 692 604 510 401 200 203 465.1
Mean 212.0 287.4 395.1 514.9 583.3 630.4 615.6 548.4 465.4 349.6 242.8 197.7 421.4

Pan Evaporation

Evaporation is affected by solar radiation, temperature, humidity and wind. With appropriate correction factors, it is sometimes used as an index of plant water-use. From 1974 to 2003, total pan evaporation between May 1 and Sept. 30 averaged 57 inches (table 11) or 0.37 inches/day (table 12). Average total monthly evaporation was greatest in June and July (13.1 inches) (table 11 and fig. 7). This corresponded to an average daily evaporation rate of about 0.43 inches (table 12).

Table 11. Total monthly evaporation (inches) from a Class-A pan at NMSU's Agricultural Science Center at Farmington, 1972-2003.

Year Apr. May June July Aug. Sept. Oct. Total*
1972 --- --- --- 14.82 11.81 9.57 4.40 ---
1973 --- --- 11.10 11.53 10.66 9.57 --- ---
1974 --- 12.99 15.36 12.87 12.25 9.33 4.59 62.8
1975 --- 9.27 12.03 12.28 12.49 8.10 7.50 54.2
1976 --- 11.78 15.45 13.76 13.11 9.06 5.89 63.2
1977 9.12 12.28 14.94 13.11 12.21 9.51 6.60 62.1
1978 9.30 9.64 12.81 14.54 13.08 9.63 7.97 59.7
1979 8.34 8.62 10.86 10.97 10.60 9.51 --- 50.6
1980 7.74 9.98 14.67 14.01 12.59 8.16 --- 59.4
1981 7.62 9.21 14.10 12.03 11.25 7.65 --- 54.2
1982 --- 10.01 12.81 12.14 9.73 7.28 --- 52.0
1983 --- 10.00 11.51 12.51 11.06 8.72 --- 53.8
1984 --- 12.15 11.66 11.74 10.43 7.84 3.29 53.8
1985 --- 8.74 12.27 12.68 11.61 6.99 4.44 52.3
1986 7.36 9.82 10.97 11.34 11.34 6.75 --- 50.2
1987 --- 6.64 11.47 12.19 10.39 8.23 3.12 48.9
1988 --- 11.55 11.06 13.05 9.74 8.55 6.16 54.0
1989 --- 12.18 12.54 13.83 11.04 9.37 --- 59.0
1990 8.80 11.56 15.48 12.74 11.35 8.82 5.77 60.0
1991 8.68 11.68 10.99 12.77 11.11 8.53 --- 55.1
1992 7.76 8.67 12.15 11.89 10.80 8.19 6.53 51.7
1993 9.66 10.52 13.94 14.78 10.17 9.11 5.57 58.5
1994 8.35 11.90 15.04 15.63 12.46 9.28 7.38 64.3
1995 7.48 9.78 12.72 13.81 11.63 9.74 7.48 57.7
1996 9.10 13.50 12.72 13.99 11.10 7.08 5.66 58.4
1997 7.37 9.33 11.84 12.36 9.59 7.78 5.80 50.9
1998 7.27 11.37 14.12 13.03 11.36 10.03 5.85 59.9
1999 8.31 10.75 13.12 11.75 8.68 8.21 7.45 52.5
2000 9.62 13.20 14.11 13.16 11.36 8.86 4.87 60.7
2001 8.45 11.35 13.92 12.57 10.93 10.85 7.29 59.6
2002 9.21 13.29 14.79 14.09 12.28 7.82 4.63 62.3
2003 8.22 11.58 14.8 15.63 12.32 9.33 6.58 63.7
Mean 8.39 10.78 13.08 13.02 11.27 8.66 5.86 56.8
*Total from May through September.

 

Fig. 7: Bar graph of average monthly pan evaporation, 1972-2003.

Figure 7. Average monthly pan evaporation at NMSU's Agricultural Science Center at Farmington, 1972-2003.

Table 12. Average daily evaporation (inches) in each month from a Class-A pan at NMSU's Agricultural Science Center at Farmington, 1972-2003.

Year Apr. May June July Aug. Sept. Oct. Mean*
1972 --- --- --- 0.478 0.381 0.319 0.142 ---
1973 --- --- 0.370 0.372 0.344 0.319 --- ---
1974 --- 0.419 0.512 0.415 0.395 0.311 0.148 0.410
1975 --- 0.299 0.401 0.396 0.403 0.270 0.242 0.354
1976 --- 0.380 0.515 0.444 0.423 0.302 0.190 0.413
1977 0.304 0.396 0.498 0.423 0.394 0.317 0.213 0.406
1978 0.310 0.311 0.427 0.469 0.422 0.321 0.257 0.390
1979 0.278 0.278 0.362 0.354 0.342 0.317 --- 0.331
1980 0.258 0.322 0.489 0.452 0.406 0.272 --- 0.388
1981 0.254 0.297 0.470 0.388 0.363 0.255 --- 0.355
1982 --- 0.323 0.427 0.392 0.314 0.243 --- 0.340
1983 --- 0.323 0.384 0.404 0.357 0.291 --- 0.351
1984 --- 0.392 0.389 0.379 0.336 0.261 0.106 0.351
1985 --- 0.282 0.409 0.409 0.375 0.233 0.143 0.341
1986 0.245 0.317 0.366 0.366 0.366 0.225 --- 0.328
1987 --- 0.214 0.382 0.393 0.335 0.274 0.101 0.320
1988 --- 0.373 0.369 0.421 0.314 0.285 0.199 0.352
1989 --- 0.393 0.418 0.446 0.356 0.312 --- 0.385
1990 0.293 0.373 0.516 0.411 0.366 0.294 0.186 0.392
1991 0.289 0.377 0.366 0.412 0.358 0.284 --- 0.360
1992 0.259 0.280 0.405 0.384 0.348 0.273 0.211 0.338
1993 0.322 0.339 0.465 0.477 0.328 0.304 0.180 0.383
1994 0.278 0.384 0.501 0.504 0.402 0.309 0.238 0.420
1995 0.249 0.315 0.424 0.445 0.375 0.325 0.241 0.377
1996 0.303 0.435 0.424 0.451 0.358 0.236 0.183 0.381
1997 0.246 0.301 0.395 0.399 0.309 0.259 0.187 0.333
1998 0.242 0.367 0.471 0.420 0.366 0.334 0.189 0.392
1999 0.277 0.347 0.437 0.379 0.280 0.274 0.240 0.343
2000 0.321 0.426 0.470 0.425 0.366 0.295 0.157 0.397
2001 0.282 0.366 0.464 0.405 0.353 0.362 0.235 0.388
2002 0.307 0.429 0.493 0.455 0.396 0.261 0.149 0.407
2003 0.274 0.374 0.493 0.504 0.397 0.311 0.212 0.416
Mean 0.280 0.348 0.436 0.420 0.363 0.289 0.189 0.371
*Mean daily evaporation from May through September.

Soil Temperature

The average daily bare soil temperature 4 inches below the surface did not exceed 50°F (the minimum seed germination temperature for many crops) until April of each year (fig. 8). In July and August, the daily mean temperature at this depth equaled or exceeded 80°F (fig. 8 and table 13). Average soil temperature extremes ranged from a low of 25.6°F in January (table 14) to a high of 101.0°F in July (table 15).

Fig. 8: Bar graph of average monthly bare soil temperature 4 inches below the surface, 1976-2003.

Figure 8. Average monthly bare soil temperature 4 inches below the surface at NMSU's Agricultural Science Center at Farmington, 1976-2003.

Table 13. Average soil temperature (°F) 4 inches below the surface at NMSU's Agricultural Science Center at Farmington, 1976-2003.

Month Mean High Mean Low Mean* Mean Extreme High Mean Extreme Low
January 35.5 31.3 33.4 41.6 25.6
February 42.8 34.8 38.8 53.1 29.6
March 54.3 40.9 47.6 64.1 34.6
April 66.1 49.5 57.8 77.1 40.1
May 78.0 59.5 68.8 88.2 48.6
June 89.3 70.2 79.8 96.6 62.1
July 95.3 75.7 85.5 101.0 68.7
August 92.9 73.5 83.2 99.0 66.1
September 83.7 65.6 74.7 93.5 56.2
October 67.3 51.9 59.6 79.0 41.9
November 49.0 39.2 44.1 59.5 32.1
December 36.9 32.2 34.6 45.9 27.0
Mean 65.9 52.0 59.0 74.9 44.4
*Average of mean high and low.

Table 14. Soil low temperature (°F) extremes in each month four inches below the bare surface at NMSU's Agricultural Science Center at Farmington, 1976-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
1976 --- --- --- --- --- --- --- --- 53 39 36 18
1977 6 22 24 32 52 73 70 73 62 43 31 20
1978 31 34 37 49 44 68 75 70 52 44 38 27
1979 19 30 38 39 49 62 70 69 68 44 32 31
1980 36 38 40 40 54 63 72 68 61 41 37 35
1981 33 31 39 40 52 56 67 71 62 43 36 28
1982 22 29 35 43 47 63 72 68 57 40 37 30
1983 26 34 38 39 47 60 64 65 58 49 33 30
1984 23 32 32 38 42 56 69 65 53 34 30 30
1985 29 22 35 37 45 60 66 64 47 41 31 24
1986 29 29 35 37 49 62 60 62 48 37 31 33
1987 28 32 31 36 41 65 75 71 61 50 38 37
1988 32 34 38 44 45 53 68 66 56 49 31 26
1989 20 33 35 45 53 65 63 65 60 38 30 24
1990 23 26 33 43 47 59 71 63 55 42 35 28
1991 23 25 37 43 50 56 71 68 58 40 35 34
1992 28 35 40 46 54 62 66 62 59 50 27 26
1993 30 34 36 39 45 63 71 57 49 34 26 22
1994 24 20 33 38 51 64 70 65 53 37 26 26
1995 28 29 34 38 45 59 62 66 --- 42 31 20
1996 22 26 32 41 54 58 58 57 44 37 35 31
1997 27 33 34 38 46 --- --- 68 57 35 32 22
1998 22 31 31 37 54 64 68 65 63 41 33 24
1999 30 29 37 40 42 63 72 67 56 48 32 25
2000 25 32 35 40 57 64 71 68 58 44 30 28
2001 24 25 35 41 46 62 69 66 63 46 27 24
2002 23 25 28 41 51 69 72 66 51 39 32 30
2003 27 30 33 40 50 65 73 70 54 45 26 24
Mean 25.6 29.6 34.6 40.1 48.6 62.1 68.7 66.1 56.2 41.9 32.1 27.0

Table 15. Soil high temperature (°F) extremes in each month four inches below the bare surface at NMSU's Agricultural Science Center at Farmington, 1976-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
1976 --- --- --- --- --- --- --- --- 107 80 64 46
1977 44 57 68 95 106 117 117 112 103 90 67 53
1978 45 51 60 88 95 108 112 110 105 86 68 45
1979 40 53 64 80 91 101 107 107 100 89 63 44
1980 38 62 65 79 89 104 106 106 92 84 65 55
1981 52 61 69 86 88 95 98 95 88 76 58 45
1982 44 53 57 78 88 99 102 99 94 78 56 47
1983 39 53 60 71 88 91 97 97 92 74 64 43
1984 37 45 62 68 91 92 97 102 94 76 61 47
1985 45 54 63 76 90 100 108 101 103 77 66 49
1986 50 59 70 78 86 97 101 102 96 72 54 44
1987 37 54 56 77 87 93 99 97 96 80 63 49
1988 36 57 68 75 88 99 98 97 91 79 66 43
1989 35 57 69 76 85 94 100 98 90 80 59 44
1990 44 55 66 75 84 95 97 94 92 78 61 45
1991 37 50 61 76 86 94 100 99 95 85 60 42
1992 38 53 60 79 85 95 96 98 88 82 53 37
1993 42 52 67 77 89 92 99 100 88 77 53 42
1994 45 52 65 80 86 95 98 99 92 75 57 43
1995 41 60 65 72 79 90 98 99 --- 70 60 50
1996 42 55 65 77 91 96 100 92 91 78 54 48
1997 45 49 64 69 84 --- --- 95 91 81 57 47
1998 39 48 64 74 90 98 102 96 90 79 54 49
1999 44 50 65 72 80 95 99 92 86 73 57 48
2000 47 49 64 78 89 92 95 94 86 76 50 42
2001 32 47 63 78 86 93 100 96 90 83 62 47
2002 39 48 67 75 90 95 99 97 90 75 56 45
2003 45 49 63 74 90 91 100 99 95 79 59 45
Mean 41.6 53.1 64.1 77.1 88.2 96.6 101.0 99.0 93.5 79.0 59.5 45.9

Growing Degree-Days

Growing degree-days (GDD) or heat units are used to rate the maturity of various plant cultivars, especially corn. Plant development is related to temperature, and each crop has an optimum temperature range for growth. That is, there is a minimum temperature below which plants will not grow (minimum cutoff or base temperature) and a maximum temperature at which plant growth rate will stabilize or decrease (maximum cutoff temperature). The average daily temperature (mean of daily minimum and maximum temperatures) minus the base temperature is equal to GDD for that day. However, if the observed minimum temperature for the day is less than the minimum cutoff temperature (COmin), then it is set equal to COmin. Correspondingly, if the observed maximum temperature exceeds the maximum cutoff temperature (COmax), then it is set equal to COmax prior to calculating the average. In corn, base and COmin is 50°F and COmax is 86°F (Eckert, 2004). Over the 35 years, total corn GDD from May 1 to Sept. 30 averaged 2,865 (table 16). Total average monthly GDD during this period ranged from a low of 400 in May (12.9/day) to a high of 711 (22.9/day) in July (fig. 9 and table 16).

Fig. 9: Bar graph of average total monthly (May-September) growing degree-days, 1969-2003.

Figure 9. Average total monthly (May-September) growing degree-days at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Table 16. Total monthly growing degree-days* from May through September and to the first fall frost (32°F) at NMSU's Agricultural Science Center at Farmington, 1969-2003.

Year May June July Aug. Sept. Total through Date of 1st Frost
Sept. 1st Frost
1969 434 510 729 744 570 2,987 3,017 Oct. 5
1970 434 555 744 744 420 2,897 2,949 Oct. 8
1971 372 600 729 713 450 2,864 2,684 Sept. 18
1972 434 615 744 713 495 3,001 3,201 Oct. 30
1973 372 640 713 713 435 2,873 2,990 Oct. 11
1974 465 645 729 698 450 2,987 3,227 Oct. 30
1975 326 525 713 667 435 2,666 2,806 Oct. 14
1976 403 585 744 698 495 2,925 2,978 Oct. 7
1977 372 675 744 729 540 3,060 3,386 Oct. 31
1978 310 570 729 667 450 2,726 2,576 Sept. 20
1979 341 510 682 667 555 2,755 2,986 Oct. 22
1980 341 570 698 682 450 2,741 2,869 Oct. 16
1981 372 600 682 651 450 2,755 2,875 Oct. 16
1982 341 525 682 698 450 2,696 2,741 Oct. 6
1983 341 495 682 729 525 2,772 2,615 Sept. 21
1984 465 555 729 713 480 2,942 3,017 Oct. 15
1985 397 600 710 692 416 2,815 2,926 Sept. 30
1986 377 574 661 693 395 2,700 2,790 Oct. 12
1987 366 592 674 646 473 2,751 2,873 Oct. 19
1988 396 607 722 697 476 2,898 2,981 Nov. 12
1989 468 565 731 670 540 2,974 3,131 Oct. 18
1990 378 635 729 673 532 2,947 3,029 Oct. 9
1991 409 557 704 701 471 2,842 3,153 Oct. 28
1992 385 536 630 639 484 2,674 2,763 Oct. 8
1993 416 538 652 615 454 2,675 2,854 Oct. 19
1994 426 628 729 746 495 3,024 3,169 Oct. 17
1995 330 516 676 729 494 2,745 2,782 Oct. 6
1996 477 612 730 695 410 2,924 2,785 Sept. 19
1997 441 563 685 670 568 2,927 3,081 Oct. 13
1998 417 499 746 716 560 2,938 2,984 Oct. 6
1999 364 554 710 655 451 2,734 2,702 Sept. 28
2000 479 640 665 663 536 2,983 3,117 Oct. 14
2001 465 591 751 691 578 3,076 3,214 Oct. 11
2002 446 625 739 674 486 2,973 3,004 Oct. 4
2003 453 586 763 730 485 3,017 3,329 Oct. 27
Mean 400 577 711 692 484 2,865 2,960 Oct. 13
*Growing degree-days/month = ∑ (Average daily temperature between COmax and COmin minus base)
• CO(max) = 86°F
• CO(min) = 50°F
• base = 50°F
Refer to text for detailed explanation

Reference Evapotranspiration

Evapotranspiration (ET) refers to the volume of water used by a crop during a given time period. It includes water that is actively transported through the plant from the roots to leaves during transpiration and water that is lost from plant and soil surfaces through evaporation. If crops are healthy and soil moisture is not limiting, plant size and weather (radiation, air temperature, humidity, and wind speed) are the primary factors affecting crop ET (Allen, et al., 1998). Reference ET (ETo) refers to the ET of a reference crop such as grass or alfalfa that is of a certain height and is growing under optimum conditions for maximum production. Since ETo has been correlated with the weather parameters referred to above, it can be calculated when these parameters are available. Correction values or crop coefficients (Kc), if available, can then be applied to ETo to estimate a particular crop's ET rates or water requirements during the season. These estimates can then be used in irrigation scheduling. Since different researchers have derived unique mathematical formulas to calculate ETo, to effectively use published Kc values for irrigation scheduling, the ETo formula used to formulate the Kc must be known.

From 1996 to 2003, average daily ETo (using WS-2 data and a modified, grass-referenced Penman formula from the New Mexico Climate Center: http://weather.nmsu.edu/pmcomp.htm) ranged from 0.08 inch/day in January and December to 0.38 inch/day in June (fig. 10). Total annual ETo averaged 80.5 inches (table 17). From May through August, the active growing season for many crops, ETo averaged 10.4 inches/month or 0.34 inch/day.

Fig. 10: Plot of average daily reference evapotranspiration (ETo), 1996-2003.

Figure 10. Average daily reference evapotranspiration (ETo) at NMSU's Agricultural Science Center at Farmington based on calculations from the New Mexico Climate Center, 1996-2003.

Table 17. Average total and average daily reference evapotranspiration* (ETo) during each month at NMSU's Agricultural Science Center at Farmington, 1996-2003.

Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Mean
  ------------------------------------------------ Total Monthly ETo -------------------------------------------------
1996 2.88 3.61 6.11 8.32 11.10 10.39 11.46 9.08 6.76 5.45 2.92 2.26 80.3
1997 1.69 3.20 7.26 6.50 9.12 10.54 10.55 7.17 7.14 5.81 3.28 2.06 74.3
1998 2.37 2.47 5.52 7.24 10.25 11.58 10.44 9.48 8.25 5.05 3.13 2.60 78.4
1999 3.36 4.36 7.27 7.29 9.62 11.43 10.16 7.93 7.59 7.02 4.83 2.66 83.5
2000 2.81 3.70 5.23 8.53 11.30 11.72 --- --- 7.93 4.75 2.42 2.26 ---
2001 2.17 3.11 --- --- --- 10.35 10.30 10.19 8.75 6.20 3.44 2.54 ---
2002 2.73 4.04 6.69 9.03 11.16 12.59 11.52 9.52 7.18 4.75 3.20 2.00 84.4
2003 2.42 3.03 5.51 8.36 10.12 11.70 12.20 8.90 7.87 5.98 2.55 2.33 81.0
Mean 2.55 3.44 6.23 7.90 10.38 11.29 10.95 8.90 7.68 5.63 3.22 2.34 80.5
  --------------------------------------------------- Average Daily ETo -----------------------------------------------
1996 0.09 0.13 0.20 0.28 0.36 0.35 0.37 0.29 0.23 0.18 0.10 0.07 0.22
1997 0.05 0.11 0.23 0.22 0.29 0.35 0.34 0.23 0.24 0.19 0.11 0.07 0.20
1998 0.08 0.09 0.18 0.24 0.33 0.39 0.34 0.31 0.28 0.16 0.10 0.08 0.21
1999 0.11 0.16 0.23 0.24 0.31 0.38 0.33 0.26 0.25 0.23 0.16 0.09 0.23
2000 0.09 0.13 0.17 0.28 0.36 0.39 --- --- 0.26 0.15 0.08 0.07 0.20
2001 0.07 0.11 --- --- --- 0.35 0.33 0.33 0.29 0.20 0.11 0.08 0.21
2002 0.09 0.14 0.22 0.30 0.36 0.42 0.37 0.31 0.24 0.15 0.11 0.06 0.23
2003 0.08 0.11 0.18 0.28 0.33 0.39 0.39 0.29 0.26 0.19 0.09 0.08 0.22
Mean 0.08 0.12 0.20 0.26 0.33 0.38 0.35 0.29 0.26 0.18 0.11 0.08 0.22
*Modified FAO-24 Penman reference ET (grass based) from New Mexico Climate Center (NMCC) web site http://weather.nmsu.edu

Metric Conversions

Data reported in figures 1-10 and tables 1-17 are in English units. The formulas used to convert English units to standard international (SI) or metric units are:

Temperature: °C = 5/9 (°F - 32)

Precipitation, pan evaporation, and ETo: mm = inches x 25.4

Wind speed: km/day = miles/day x 1.609

Solar radiation: joules/m2 /day = Langleys x (4.19 x 104)

Growing degree-days (°C based) = growing degree-days (°F based) x 5/9

Literature Cited

Allen, R.G., L.S. Pereira, D. Raes, and M. Smith. 1998. Crop evapotranspiration. Guidelines for computing crop water requirements. FAO Irrig. Drain Pap. 56.

Eckert, D.J. Growing Degree Days as a Method of Rating the Maturity of Corn Hybrids. Ohio State Univ. Ext. Ag. Facts. AGF-101-90 http://ohioline.osu.edu/agf-fact/0101.html No posting date provided.

Longstroth, M. 2001. Assessing Frost Damage to Fruit Buds of Fruit Trees. Michigan State Univ. Extension. Van Buren County. http://www.msue.msu.edu/vanburen/frstflw.htm Posted June 14, 1996.


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Printed and electronically distributed April 2006, Las Cruces, NM.