Harrah climate

Harrah Frost Dates and Growing Season

NOAA 1991-2020 normals for Wapato, 10.1 km from Harrah, elevation 841 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wapato. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around April 21 and the first fall freeze around October 15, a growing season of about 176 days.

Median at 36°F
last May 6, first October 5
Median at 32°F
last April 21, first October 15
Median at 28°F
last March 31, first October 26

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FMay 25May 17May 13May 9May 6May 3Apr 30Apr 27Apr 22
32°FMay 7May 2Apr 28Apr 25Apr 21Apr 18Apr 14Apr 9Apr 1
28°FApr 21Apr 12Apr 6Apr 2Mar 31Mar 28Mar 23Mar 17Mar 10
24°FMar 27Mar 21Mar 15Mar 11Mar 8Mar 5Mar 2Feb 27Feb 21
20°FMar 12Mar 6Mar 2Feb 27Feb 23Feb 19Feb 14Feb 7Jan 24
16°FMar 2Feb 26Feb 21Feb 14Feb 7Jan 31Jan 22Jan 13Jan 3

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 25Sep 29Oct 1Oct 3Oct 5Oct 7Oct 10Oct 13Oct 16
32°FOct 4Oct 7Oct 10Oct 12Oct 15Oct 17Oct 19Oct 22Oct 27
28°FOct 13Oct 17Oct 21Oct 24Oct 26Oct 28Oct 31Nov 3Nov 9
24°FOct 23Oct 28Oct 30Nov 1Nov 5Nov 8Nov 12Nov 16Nov 23
20°FOct 31Nov 5Nov 8Nov 12Nov 16Nov 21Nov 25Nov 30Dec 7
16°FNov 8Nov 16Nov 21Nov 25Nov 30Dec 3Dec 10Dec 19Dec 29

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F168162158154150146142137131
32°F199191186181176172168163156
28°F233225219214210205199194186
24°F263256251246241237232227218
20°F301291282275269264258251243
16°F338325316308300293284275265

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
99% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
5,427
Cooling degree days, base 65°F
817
Growing degree days, base 40°F
5,320
Growing degree days, base 45°F
4,079
Growing degree days, base 50°F
3,018
Growing degree days, base 55°F
2,126
Growing degree days, base 60°F
1,391

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,02800
February78701
March628021
April3953107
May18143331
June53121518
July6307766
August10265721
September9076437
October4172112
November77705
December1,05700

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 10.1 km from Harrah. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00458959 (Wapato). Public domain.