1998 Weather Report

Erik B. G. Feibert and Clinton C. Shock
Malheur Experiment Station
Oregon State University
Ontario, OR

Introduction

Air temperature and precipitation have been recorded daily at the Malheur Experiment Station since July 20, 1942. Installation of additional equipment in 1948 allowed for evaporation and wind measurements. A soil thermometer at 4-in depth was added in 1967. A biophenometer, to monitor degree-days, and pyranometers, to monitor solar and photosynthetically active radiation, were added in 1985.

Since 1962, the Malheur Experiment Station has participated in the Cooperative Weather Station system of the National Weather Service. The daily readings from the station are reported to the National Weather Service forecast office in Boise, Idaho.

On June 1, 1992, in cooperation with the U.S. Department of the Interior, Bureau of Reclamation, a fully automated weather station, connected by satellite to the Northwest Cooperative Agricultural Weather Network (AgriMet) computer in Boise, Idaho, began transmitting data from Malheur Experiment Station. The automated station monitors air temperature, relative humidity, dew point temperature, precipitation, wind run, wind speed, wind direction, solar radiation, and soil temperature at 8-in and 20-in depths. Stored data is transmitted via satellite to the Boise computer every 4 hours and is used to calculate daily Malheur County crop water-use estimates. The AgriMet database may be accessed via computer modem through the Internet at: www.pn.usbr.gov/agrimet.

Starting on June 1997, the daily weather data and the monthly weather summaries have been posted on the Malheur Experiment Station web site on the Internet at: www.cropinfo.net.

Methods

The ground under and around the weather stations has been covered with turf grass since October 17, 1997. The grass is irrigated with subsurface drip irrigation. The ground around and under the weather stations before October 17, 1997, was bare. The weather data is recorded each day at 8:00 a.m. All data pertains to the preceding 24-hour period except the 8:00 a.m. air temperature.

Evaporation is measured from April through October as inches of water evaporated from a standard 10-in deep by 47.5-in diameter pan over 24 hours. Wind run is measured as total wind movement in miles over a 24 hour period measured at 24 inches above ground level. Weather data averages in the tables refer to the years preceding and up to, but not including the current year.

1998 Weather

The 1998 growing season started out cooler and wetter than normal. The month of May had 4.55 in of precipitation compared to the 55-year mean of 1.02 in (Table 1). May had 29 percent fewer and June had 18 percent fewer growing degree-days (50 -86 °F) than the previous 10 year mean (Table 2). Pan-evaporation for May totaled 5.9 in, 34 percent lower than the 10-year mean and 22 percent lower than the 48-year mean (Table 3).

A severe hail storm occurred on July 4 at 7:31 p.m. in an approximately 2-mile wide and 8-mile long zone running from about 3 miles west of the station through the center of Ontario at the level of Ontario High School. Major crop damage resulted from the hail. The rain gauge at the station recorded 0.93 in of precipitation for the half-hour duration of the hail storm. Actual precipitation could have been higher because hail tends to bounce out of the rain gauge.

The months of July and August were hotter than normal. Weather station data recorded 11 days with maximum air temperatures of 100 °F or higher compared to the 50-year mean of 5 days. There were far more degree-days in the above optimal range (86 to 104 °F) in 1998 compared to the previous 8-year mean; 70 percent more in July, 29 percent more in August, and 39 percent more for the whole year (Table 4).

Mean monthly maximum air temperatures were close to the 10-year and 53-year means (Table 5). The total accumulated growing degree days (50-86 °F) was close to the 10-year mean (Table 2).

The mean monthly maximum and minimum 4-in soil temperatures in January and February were higher than the 10-year and 31-year means (Table 6). From March through October the mean monthly maximum and minimum 4-in soil temperatures were lower than the 10-year and 31-year means. The difference in soil temperature between 1998 and the mean is probably caused by the installation of turf around the weather station in October of 1997. The soil remains warmer in winter and cooler in spring and summer under the turf compared to the bare ground in the past.

Total pan-evaporation for April through October was 51.4 inches, lower than the 10-year mean and close to the 48-year mean (Table 3).

The last spring frost ([32 °F) occurred on April 18, eight days earlier than the 20-year mean date of April 26; the first fall frost occurred on October 17, thirteen days later than normal (Table 7).

The monthly wind-run totals for the months of April through October were higher than the 50-year mean (Table 8).

The weather in 1998 did not exceed any record weather events recorded over the 54-year history for the Malheur Experiment Station except that May was the wettest month on record (Table 9). The highest temperature for the year was 105 °F on August 6 (Table 5). The lowest temperature for the year was -2 °F on December 23. Total precipitation was 15.28 in for the year, 51 percent higher than the 10-year station average and 49 percent higher than the 55-year station average (Table 1). Total snowfall for 1996 was 14.6 in, slightly lower than the 10-year and 54-year means, respectively (Table 10).

Table 1. Monthly precipitation at the Malheur Experiment Station, Oregon State University, Ontario, OR.

Year

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
----------------------------------------------------- inches -----------------------------------------------------
1988 1.25 0.14 0.26 0.75 0.50 0.65 0.06 0.00 0.04 0.00 2.45 1.48 7.58
1989 0.88 1.27 2.17 0.50 0.60 0.77 0.08 0.94 0.83 0.86 0.24 0.01 9.15
1990 0.44 0.35 0.72 1.52 1.70 0.36 0.04 0.61 0.00 0.49 0.69 0.29 7.21
1991 0.59 0.44 0.88 0.81 1.89 1.09 0.01 0.04 0.35 1.01 1.71 0.43 9.25
1992 0.58 1.36 0.25 0.74 0.21 1.43 0.36 0.01 0.09 0.95 1.15 1.51 8.64
1993 2.35 1.02 2.41 2.55 0.70 1.55 0.18 0.50 0.00 0.80 0.64 0.60 13.30
1994 1.20 0.57 0.05 1.02 1.62 0.07 0.19 0.00 0.15 1.23 2.46 1.49 10.05
1995 2.67 0.28 1.58 1.16 1.41 1.60 1.10 0.13 0.07 0.57 0.88 2.56 14.01
1996 0.97 0.86 1.03 1.19 2.39 0.12 0.32 0.31 0.59 0.97 1.18 2.76 12.69
1997 2.13 0.17 0.25 0.66 0.67 0.86 1.40 0.28 0.40 0.43 1.02 0.94 9.21
1998 2.26 1.45 0.95 1.43 4.55 0.36 1.06 0.00 1.00 0.04 1.07 1.11 15.28
10-yr avg 1.31 0.65 0.96 1.09 1.17 0.85 0.37 0.28 0.25 0.73 1.27 1.21 10.14
55-yr avg 1.33 0.92 0.96 0.81 1.02 0.8 0.25 0.42 0.5 0.71 1.2 1.35 10.28

Table 2. Cumulative monthly growing degree-days (50-86 °F). Malheur Experiment Station, Oregon State University, Ontario, OR, 1988-1997.

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1988 0 5 56 236 554 1139 2050 2741 3117 3426 3446 3446
1989 0 0 13 197 469 1018 1751 2332 2721 2838 2852 2852
1990 2 9 88 327 588 1085 1819 2454 3039 3077 3077 3077
1991 0 13 29 153 365 754 1530 2248 2684 2878 2879 2879
1992 0 13 119 321 803 1377 2016 2720 3105 3279 3283 3283
1993 0 0 23 104 527 885 1349 1873 2281 2533 2539 2539
1994 0 2 94 283 652 1175 1969 2743 3252 3396 3398 3398
1995 0 29 61 167 460 893 1573 2161 2633 2734 2737 2747
1996 0 5 58 193 436 929 1687 2345 2709 2903 2921 2923
1997 4 4 85 202 621 1130 1791 2497 2977 3134 3154 3154
1998 0 2 54 166 400 805 1607 2356 2871 3022 3038 3042
10-yr avg 1 8 63 218 548 1034 1754 2411 2852 3020 3029 3030

Table 3. Pan-evaporation totals. Malheur Experiment Station, Oregon State University, Ontario, OR, 1998.

Totals April May Jun Jul Aug Sep Oct Total
Daily ------------------------------------------- inches --------------------------------------------
Mean 0.18 0.19 0.28 0.37 0.36 0.22 0.15  
Max. 0.27 0.35 0.41 0.53 0.54 0.32 0.3  
Min. 0.1 0 0.1 0.1 0.25 0.06 0.07  
Annual ---------------------------------------------- inches ------------------------------------------
1998 5.12 5.91 8.27 9.9 11.21 6.5 4.52 51.43
10-yr avg 6.10 9.01 9.81 11.83 10.42 7.59 4.36 59.12
48-yr avg 5.54 7.60 8.80 11.10 9.50 6.19 3.09 51.15

Table 4. Monthly degree-days (86 -104 °F). Malheur Experiment Station, Oregon State University, Ontario, OR, 1990-1998.

Year Apr May Jun Jul Aug Sep Oct Total
1990 0 0 13 56 41 14 0 124
1991 0 0 2 41 36 4 0 83
1992 0 5 20 23 54 2 0 104
1993 0 4 4 2 11 5 0 26
1994 0 2 16 68 54 7 0 147
1995 0 0 4 23 22 7 0 56
1996 0 0 5 54 32 4 0 95
1997 0 4 0 27 31 5 0 67
1998 0 0 0 63 45 14 0 122
8-yr avg 0 2 8 37 35 6 0 88

Table 5. Monthly air temperature. Malheur Experiment Station, Oregon State University, Ontario, OR, 1998.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

  ------------------------------------------------------------------------ oF ------------------------------------------------------------------
Max. 51 37 58 41 68 49 81 47 85 52 91 58 103 69 105 64 97 65 83 46 63 42 60 44
Min. 28 14 41 22 40 24 51 31 49 38 66 34 79 56 84 48 68 43 56 23 41 24 15 -2
1998 avg 41 29 48 32 55 34 62 38 68 46 78 48 95 61 93 57 84 52 66 36 52 36 37 22
10-yr avg 35 20 43 23 56 31 65 38 74 46 82 53 90 57 89 54 81 46 67 35 47 27 38 20
53-yr avg 35 19 43 25 55 31 64 37 74 45 82 52 91 57 90 55 80 46 65 36 48 28 37 22

Table 6. Monthly 4-in soil temperature. Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1998.

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  High low High low High low High low High low High low High low High low High low High low High low High low
  ------------------------------------------------------ °F ------------------------------------------------
Max. 42 41 44 44 58 48 59 53 65 60 73 63 78 72 78 71 73 69 65 62 50 48 44 44
Min. 37 36 41 41 41 41 45 42 54 53 60 54 67 60 68 64 63 61 48 46 43 42 28 45
1998 mean 38 38 42 42 45 44 51 46 59 55 65 59 74 68 73 68 69 64 55 51 45 44 35 46
10-yr mean 33 32 39 35 51 42 62 50 73 59 81 67 89 74 87 74 78 66 63 53 45 40 35 47
31-yr mean 33 32 38 34 51 41 62 48 74 58 82 67 90 75 88 74 77 64 61 51 44 39 34 48

Table 7. Last and first frost ([32 °F) dates and number of frost-free days. Malheur Experiment Station, Oregon State University, Ontario, OR, 1976-1998.

Year

Date of last frost Date of first frost

Total frost-free days

Spring Fall
1976 Apr 23 Oct 5 165
1977 Apr 20 Sep 22 155
1978 Apr 23 Oct 14 174
1979 Mar 20 Oct 27 221
1980 Apr 13 Oct 17 187
1981 Apr 14 Oct 1 170
1982 May 5 Oct 5 153
1983 Apr 27 Sep 20 146
1984 May 7 Sep 25 141
1985 May 13 Sep 30 140
1986 May 23 Oct 12 142
1987 Apr 21 Oct 11 173
1988 May 2 Oct 30 181
1989 May 19 Sep 13 117
1990 May 8 Oct 7 152
1991 Apr 30 Oct 4 157
1992 Apr 24 Sep 14 143
1993 Apr 20 Oct 11 174
1994 Apr 15 Oct 6 174
1995 Apr 16 Sep 22 159
1996 May 6 Sep 23 139
1997 May 3 Oct 8 158
1998 Apr 18 Oct 17 182
Average April 26 October 4 161

Table 8. Daily wind-run totals and monthly totals. Malheur Experiment Station, Oregon State University, Ontario, OR, 1998.

Total

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Daily

-------------------------------------------- miles ------------------------------------------------

Max.

193 196 304 132 138 151 92 107 104 232 259 225

Min.

14 21 31 32 19 18 23 25 20 23 16 24

Average

55 83 85 74 61 63 52 56 45 69 72 74

Annual

---------------------------------------------- miles -------------------------------------------------

1998

1,704 2,332 2,634 2,226 1,890 1,902 1,619 1,722 1,350 2,136 2,169 2,279

10-yr average

      2247 2369 1983 1774 1597 1562 1660    

50-yr average

      2110 1891 1531 1449 1291 1228 1252    

Table 9. Record weather events at the Malheur Experiment Station, Oregon State University, Ontario, OR.

Record event Measurement Date

Greatest annual precipitation

16.87 in 1983

Greatest monthly precipitation

4.55 in May 1998

Greatest 24-hour precipitation

1.52 in Sep 14, 1959

Greatest annual snowfall

40 in 1955

Greatest 24-hour snowfall

10 in Nov 30, 1975

Earliest snowfall

1 in Oct 25, 1970

Highest air temperature

108 oF Aug 4, 1961

Total days with max. air temp. m 100 °F

17 days 1971

Lowest air temperature

-26 °F Jan 21 and 22, 1962

Total days with min. air temp. [ 0 °F

35 days 1985

Lowest 4-in soil temperature

12 °F Dec 24, 25, and 26, 1990

Table 10. Annual snowfall totals at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1988-1997.

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

10-yr avg 54-yr avg
--------------------------------------------- inches ---------------------------------------------
34.80 25.10 5.70 7.50 15.50 36.00 32.00 15.00 14.50 5.80 14.60 19.19 18.88