Custer climate

Custer Frost Dates and Growing Season

NOAA 1991-2020 normals for Custer, 1.3 km from Custer, elevation 5480 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Custer. 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 18 and the first fall freeze around September 28, a growing season of about 129 days.

Median at 36°F
last May 30, first September 17
Median at 32°F
last May 18, first September 28
Median at 28°F
last May 6, first October 4

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 15Jun 8Jun 4Jun 1May 30May 27May 24May 21May 16
32°FJun 1May 29May 25May 21May 18May 15May 12May 9May 5
28°FMay 22May 16May 12May 9May 6May 3May 1Apr 28Apr 23
24°FMay 8May 4Apr 30Apr 28Apr 25Apr 21Apr 19Apr 15Apr 11
20°FApr 30Apr 25Apr 21Apr 17Apr 14Apr 11Apr 7Apr 4Mar 31
16°FApr 21Apr 16Apr 12Apr 8Apr 5Apr 1Mar 29Mar 23Mar 15

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 3Sep 6Sep 10Sep 14Sep 17Sep 20Sep 22Sep 26Oct 1
32°FSep 10Sep 17Sep 21Sep 25Sep 28Sep 30Oct 2Oct 5Oct 10
28°FSep 20Sep 25Sep 29Oct 1Oct 4Oct 7Oct 11Oct 14Oct 19
24°FSep 27Oct 3Oct 6Oct 10Oct 13Oct 16Oct 19Oct 24Oct 29
20°FOct 6Oct 11Oct 16Oct 18Oct 22Oct 25Oct 30Nov 2Nov 7
16°FOct 14Oct 19Oct 23Oct 27Nov 1Nov 4Nov 8Nov 12Nov 18

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°F1281211161121091051019690
32°F149142138134129125121117110
28°F169163158153149144140135128
24°F190183177173169165161154146
20°F213204198194189186181176169
16°F233224218213208203197192184

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
7,585
Cooling degree days, base 65°F
308
Growing degree days, base 40°F
3,725
Growing degree days, base 45°F
2,745
Growing degree days, base 50°F
1,922
Growing degree days, base 55°F
1,239
Growing degree days, base 60°F
691

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18900
February1,07400
March93606
April723022
May4424127
June15938337
July41134558
August53104517
September22528285
October630161
November92108
December1,19200

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 1.3 km from Custer. 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 USC00392087 (Custer). Public domain.