Alma climate

Alma Frost Dates and Growing Season

NOAA 1991-2020 normals for Harlan CO Lake, 12.7 km from Alma, elevation 2010 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Harlan CO Lake. 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 25 and the first fall freeze around October 14, a growing season of about 170 days.

Median at 36°F
last May 3, first October 5
Median at 32°F
last April 25, first October 14
Median at 28°F
last April 14, first October 23

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 15May 11May 8May 5May 3May 1Apr 30Apr 26Apr 21
32°FMay 7May 3May 1Apr 28Apr 25Apr 22Apr 19Apr 15Apr 10
28°FApr 29Apr 24Apr 21Apr 17Apr 14Apr 11Apr 8Apr 5Mar 31
24°FApr 20Apr 15Apr 11Apr 7Apr 4Apr 2Mar 31Mar 25Mar 19
20°FApr 12Apr 6Apr 2Mar 31Mar 26Mar 22Mar 18Mar 14Mar 7
16°FApr 4Mar 30Mar 24Mar 19Mar 15Mar 12Mar 7Mar 4Feb 27

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 23Sep 26Sep 29Oct 2Oct 5Oct 8Oct 11Oct 14Oct 17
32°FSep 28Oct 3Oct 8Oct 12Oct 14Oct 17Oct 19Oct 22Oct 25
28°FOct 6Oct 14Oct 18Oct 20Oct 23Oct 24Oct 27Oct 31Nov 4
24°FOct 18Oct 22Oct 25Oct 28Oct 31Nov 2Nov 5Nov 8Nov 14
20°FOct 24Oct 31Nov 2Nov 5Nov 8Nov 12Nov 16Nov 20Nov 26
16°FNov 1Nov 5Nov 10Nov 14Nov 18Nov 22Nov 25Nov 30Dec 5

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°F168164160156153150146141136
32°F191184179174170167163159151
28°F209203198194190186181176169
24°F229223217213208204200196188
20°F249241236230227221217211204
16°F270262255250245241235228219

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
5,788
Cooling degree days, base 65°F
1,181
Growing degree days, base 40°F
5,843
Growing degree days, base 45°F
4,643
Growing degree days, base 50°F
3,579
Growing degree days, base 55°F
2,646
Growing degree days, base 60°F
1,849

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18900
February95205
March732039
April4287131
May17561363
June20240671
July1395858
August4323784
September80140514
October37216188
November749026
December1,08601

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 12.7 km from Alma. 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 USC00253595 (Harlan CO Lake). Public domain.