Tillman County climate

Tillman County Frost Dates and Growing Season

NOAA 1991-2020 normals for Altus AFB, 4.9 km from Tillman County, elevation 1267 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Altus AFB. 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 March 26 and the first fall freeze around November 10, a growing season of about 229 days.

Median at 36°F
last April 8, first November 2
Median at 32°F
last March 26, first November 10
Median at 28°F
last March 11, first November 21

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 24Apr 19Apr 15Apr 11Apr 8Apr 5Apr 1Mar 28Mar 22
32°FApr 14Apr 7Apr 3Mar 31Mar 26Mar 22Mar 18Mar 13Mar 8
28°FApr 1Mar 25Mar 19Mar 15Mar 11Mar 8Mar 5Mar 1Feb 23
24°FMar 17Mar 11Mar 7Mar 3Feb 28Feb 25Feb 19Feb 13Feb 4
20°FMar 6Mar 1Feb 25Feb 19Feb 13Feb 8Feb 1Jan 24Jan 13
16°FFeb 27Feb 17Feb 9Feb 2Jan 27Jan 21Jan 14Jan 4Dec 23

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 20Oct 24Oct 28Oct 31Nov 2Nov 4Nov 7Nov 11Nov 15
32°FOct 26Oct 31Nov 4Nov 7Nov 10Nov 13Nov 16Nov 20Nov 27
28°FNov 2Nov 9Nov 13Nov 17Nov 21Nov 25Nov 29Dec 2Dec 8
24°FNov 12Nov 20Nov 25Nov 29Dec 2Dec 6Dec 10Dec 15Dec 22
20°FNov 23Dec 1Dec 6Dec 11Dec 17Dec 22Dec 29Jan 4Jan 13
16°FDec 3Dec 10Dec 17Dec 23Dec 29Jan 4Jan 10Jan 21Feb 2

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°F227220215211207203198193185
32°F250243238233229223218212205
28°F276267262257252247242235226
24°F309296289284277272267260250
20°F339329321313306301292285274
16°F365362348341334329321311301

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
99% of years
16°F or colder
82% 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
2,975
Cooling degree days, base 65°F
2,496
Growing degree days, base 40°F
8,885
Growing degree days, base 45°F
7,307
Growing degree days, base 50°F
5,877
Growing degree days, base 55°F
4,601
Growing degree days, base 60°F
3,473

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January721025
February548259
March34919201
April14266383
May24252693
June0481931
July06251,090
August06001,065
September8341783
October115102460
November3879154
December682034

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 4.9 km from Tillman County. 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 USW00003981 (Altus AFB). Public domain.