Altus climate

Altus Frost Dates and Growing Season

NOAA 1991-2020 normals for Ozark 2, 12.1 km from Altus, elevation 830 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ozark 2. 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 30 and the first fall freeze around November 6, a growing season of about 222 days.

Median at 36°F
last April 13, first October 29
Median at 32°F
last March 30, first November 6
Median at 28°F
last March 15, first November 18

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 30Apr 25Apr 21Apr 17Apr 13Apr 9Apr 5Mar 31Mar 25
32°FApr 17Apr 10Apr 5Apr 2Mar 30Mar 25Mar 21Mar 17Mar 10
28°FApr 4Mar 29Mar 24Mar 19Mar 15Mar 11Mar 7Mar 3Feb 25
24°FMar 23Mar 17Mar 12Mar 8Mar 4Mar 1Feb 25Feb 19Feb 12
20°FMar 13Mar 6Mar 3Feb 27Feb 20Feb 15Feb 9Feb 2Jan 25
16°FMar 5Feb 25Feb 15Feb 8Feb 3Jan 30Jan 24Jan 17Jan 6

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 15Oct 19Oct 23Oct 27Oct 29Nov 1Nov 3Nov 6Nov 11
32°FOct 23Oct 29Nov 1Nov 3Nov 6Nov 9Nov 14Nov 18Nov 23
28°FNov 2Nov 6Nov 10Nov 14Nov 18Nov 22Nov 26Dec 1Dec 6
24°FNov 10Nov 17Nov 23Nov 27Dec 1Dec 4Dec 8Dec 14Dec 22
20°FNov 22Nov 30Dec 4Dec 11Dec 16Dec 20Dec 26Jan 1Jan 10
16°FDec 4Dec 12Dec 19Dec 25Dec 30Jan 4Jan 9Jan 16Jan 29

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°F222214208203198194189183176
32°F249240233227222218213207198
28°F271262257252246241236229220
24°F298288283275269264259252243
20°F330319311304297291284277266
16°F361347339334326319311302292

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
91% 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
3,548
Cooling degree days, base 65°F
1,820
Growing degree days, base 40°F
7,763
Growing degree days, base 45°F
6,270
Growing degree days, base 50°F
4,930
Growing degree days, base 55°F
3,741
Growing degree days, base 60°F
2,704

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January828018
February628137
March4478133
April20439304
May51145560
June2347795
July0490955
August0467931
September17255689
October16964372
November4595109
December744027

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 12.1 km from Altus. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00035512 (Ozark 2). Public domain.