White River climate

White River Frost Dates and Growing Season

NOAA 1991-2020 normals for Cedar Butte, 22.1 km from White River, elevation 2355 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cedar Butte. 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 May 6 and the first fall freeze around October 4, a growing season of about 151 days.

Median at 36°F
last May 17, first September 27
Median at 32°F
last May 6, first October 4
Median at 28°F
last April 29, first October 14

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 31May 27May 23May 20May 17May 14May 11May 7May 3
32°FMay 22May 17May 13May 10May 6May 4May 1Apr 28Apr 24
28°FMay 12May 7May 4May 1Apr 29Apr 26Apr 22Apr 18Apr 13
24°FMay 2Apr 27Apr 24Apr 20Apr 17Apr 14Apr 10Apr 6Apr 2
20°FApr 22Apr 17Apr 14Apr 10Apr 7Apr 4Apr 2Mar 29Mar 21
16°FApr 14Apr 9Apr 5Apr 2Mar 30Mar 27Mar 22Mar 17Mar 11

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 14Sep 20Sep 22Sep 25Sep 27Sep 29Oct 1Oct 4Oct 8
32°FSep 22Sep 26Sep 30Oct 1Oct 4Oct 6Oct 10Oct 14Oct 19
28°FSep 29Oct 3Oct 7Oct 11Oct 14Oct 17Oct 20Oct 24Oct 29
24°FOct 4Oct 11Oct 16Oct 19Oct 22Oct 25Oct 29Nov 1Nov 6
20°FOct 15Oct 21Oct 25Oct 28Nov 1Nov 3Nov 6Nov 10Nov 15
16°FOct 24Oct 29Nov 1Nov 6Nov 8Nov 10Nov 14Nov 17Nov 23

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°F151145140137134130126122115
32°F170165159155151147142138132
28°F189183177173169165160155148
24°F208201196192188184178173166
20°F227219214210206202197192184
16°F249240234229223217213207200

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
100% 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
6,763
Cooling degree days, base 65°F
916
Growing degree days, base 40°F
5,147
Growing degree days, base 45°F
4,035
Growing degree days, base 50°F
3,060
Growing degree days, base 55°F
2,215
Growing degree days, base 60°F
1,500

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,28201
February1,07503
March878025
April563378
May26330266
June55136532
July5332792
August13290742
September116112456
October47311142
November849022
December1,19201

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 22.1 km from White River. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00391539 (Cedar Butte). Public domain.