Alliance climate

Alliance Frost Dates and Growing Season

NOAA 1991-2020 normals for Alliance Muni AP, 7.8 km from Alliance, elevation 3924 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Alliance Muni AP. 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 22 and the first fall freeze around September 22, a growing season of about 122 days.

Median at 36°F
last June 2, first September 13
Median at 32°F
last May 22, first September 22
Median at 28°F
last May 12, first October 1

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°FJun 19Jun 14Jun 8Jun 5Jun 2May 31May 27May 24May 20
32°FJun 5May 31May 28May 25May 22May 19May 16May 13May 10
28°FMay 25May 20May 16May 14May 12May 9May 6May 4Apr 30
24°FMay 15May 11May 7May 4May 2Apr 30Apr 27Apr 23Apr 19
20°FMay 6May 1Apr 29Apr 26Apr 22Apr 19Apr 16Apr 12Apr 6
16°FApr 27Apr 22Apr 18Apr 14Apr 11Apr 7Apr 3Mar 30Mar 21

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 1Sep 4Sep 7Sep 11Sep 13Sep 16Sep 19Sep 22Sep 26
32°FSep 7Sep 13Sep 16Sep 19Sep 22Sep 25Sep 28Oct 1Oct 4
28°FSep 16Sep 22Sep 25Sep 28Oct 1Oct 3Oct 5Oct 8Oct 12
24°FSep 26Sep 30Oct 4Oct 6Oct 9Oct 12Oct 14Oct 17Oct 21
20°FOct 4Oct 10Oct 13Oct 15Oct 17Oct 19Oct 22Oct 25Oct 29
16°FOct 12Oct 16Oct 18Oct 21Oct 24Oct 26Oct 29Nov 1Nov 6

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°F11911411010710399949080
32°F140133129125122118114109101
28°F156151147143140137133129123
24°F176170165161158154151145140
20°F197190184180176173169164158
16°F219211205200195191186181175

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
7,395
Cooling degree days, base 65°F
561
Growing degree days, base 40°F
4,261
Growing degree days, base 45°F
3,240
Growing degree days, base 50°F
2,371
Growing degree days, base 55°F
1,640
Growing degree days, base 60°F
1,036

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,26800
February1,08200
March88709
April644036
May3639177
June9090452
July11234688
August26184623
September19144322
October605161
November94804
December1,28200

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 7.8 km from Alliance. 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 USW00024044 (Alliance Muni AP). Public domain.