Altus climate

Altus Frost Dates and Growing Season

NOAA 1991-2020 normals for Altus Irig Rsch Stn, 5.3 km from Altus, elevation 1380 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Altus Irig Rsch Stn. 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 5 and the first fall freeze around November 2, a growing season of about 210 days.

Median at 36°F
last April 15, first October 24
Median at 32°F
last April 5, first November 2
Median at 28°F
last March 24, first November 10

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 29Apr 25Apr 22Apr 18Apr 15Apr 12Apr 9Apr 6Apr 2
32°FApr 21Apr 16Apr 12Apr 9Apr 5Apr 2Mar 31Mar 26Mar 20
28°FApr 8Apr 3Mar 31Mar 28Mar 24Mar 19Mar 15Mar 10Mar 4
24°FMar 28Mar 23Mar 18Mar 13Mar 9Mar 6Mar 2Feb 27Feb 22
20°FMar 15Mar 10Mar 5Mar 2Feb 27Feb 24Feb 20Feb 15Feb 5
16°FMar 8Mar 2Feb 26Feb 21Feb 16Feb 10Feb 4Jan 27Jan 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°FOct 10Oct 15Oct 19Oct 21Oct 24Oct 26Oct 29Nov 1Nov 5
32°FOct 19Oct 23Oct 27Oct 30Nov 2Nov 5Nov 7Nov 11Nov 16
28°FOct 25Oct 31Nov 4Nov 7Nov 10Nov 14Nov 18Nov 22Nov 28
24°FNov 2Nov 8Nov 14Nov 18Nov 22Nov 26Nov 29Dec 2Dec 7
20°FNov 13Nov 21Nov 25Nov 29Dec 3Dec 7Dec 12Dec 16Dec 24
16°FNov 24Dec 1Dec 6Dec 12Dec 18Dec 23Dec 29Jan 4Jan 15

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°F210204198195191188184179172
32°F233224219214210206202197189
28°F258249243237232227222216209
24°F281273267261256251246240231
20°F309299291286281275269262253
16°F342328320313306301294286276

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
3,351
Cooling degree days, base 65°F
2,250
Growing degree days, base 40°F
8,331
Growing degree days, base 45°F
6,810
Growing degree days, base 50°F
5,448
Growing degree days, base 55°F
4,237
Growing degree days, base 60°F
3,172

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January795011
February614031
March4089158
April16446343
May30212647
June1458907
July05921,057
August05531,018
September13308745
October14667395
November4325119
December749016

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 5.3 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 USC00340179 (Altus Irig Rsch Stn). Public domain.