Cheyenne climate

Cheyenne Frost Dates and Growing Season

NOAA 1991-2020 normals for Cheyenne 6SW Mesonet, 9.1 km from Cheyenne, elevation 2277 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cheyenne 6SW Mesonet. 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 3 and the first fall freeze around November 3, a growing season of about 212 days.

Median at 36°F
last April 13, first October 25
Median at 32°F
last April 3, first November 3
Median at 28°F
last March 22, first November 12

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°FApr 28Apr 24Apr 20Apr 16Apr 13Apr 10Apr 7Apr 3Mar 29
32°FApr 19Apr 13Apr 9Apr 6Apr 3Mar 31Mar 27Mar 22Mar 16
28°FApr 9Apr 3Mar 31Mar 26Mar 22Mar 18Mar 13Mar 9Mar 3
24°FMar 30Mar 24Mar 18Mar 13Mar 9Mar 6Mar 2Feb 28Feb 20
20°FMar 18Mar 11Mar 7Mar 3Mar 1Feb 25Feb 20Feb 13Feb 2
16°FMar 7Mar 2Feb 26Feb 21Feb 14Feb 9Feb 2Jan 24Jan 13

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°FOct 10Oct 16Oct 19Oct 21Oct 25Oct 28Oct 31Nov 4Nov 7
32°FOct 18Oct 24Oct 28Nov 1Nov 3Nov 6Nov 9Nov 13Nov 20
28°FOct 25Nov 1Nov 5Nov 9Nov 12Nov 15Nov 19Nov 24Nov 30
24°FNov 1Nov 8Nov 13Nov 18Nov 22Nov 26Dec 1Dec 5Dec 11
20°FNov 13Nov 20Nov 25Nov 29Dec 3Dec 7Dec 13Dec 19Dec 29
16°FNov 23Dec 1Dec 6Dec 12Dec 17Dec 24Dec 31Jan 6Jan 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°F214206201197193188184178170
32°F237229223217212208203196189
28°F258250244239234228223216208
24°F282272265260255249244237228
20°F311301293286279273267259248
16°F347333324315307300294286275

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
98% 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
3,707
Cooling degree days, base 65°F
1,838
Growing degree days, base 40°F
7,701
Growing degree days, base 45°F
6,227
Growing degree days, base 50°F
4,896
Growing degree days, base 55°F
3,723
Growing degree days, base 60°F
2,703

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January821015
February650246
March45410139
April22538291
May65160561
June1351799
July0524988
August0451916
September22237665
October19662357
November4885101
December784018

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 9.1 km from Cheyenne. 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 USC00341743 (Cheyenne 6SW Mesonet). Public domain.