Sulphur climate

Sulphur Frost Dates and Growing Season

NOAA 1991-2020 normals for Chickasaw Nra, 1.3 km from Sulphur, elevation 1047 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chickasaw Nra. 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 4 and the first fall freeze around October 31, a growing season of about 208 days.

Median at 36°F
last April 17, first October 22
Median at 32°F
last April 4, first October 31
Median at 28°F
last March 23, first November 9

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 1Apr 27Apr 23Apr 20Apr 17Apr 14Apr 10Apr 5Apr 1
32°FApr 22Apr 17Apr 12Apr 7Apr 4Apr 1Mar 29Mar 24Mar 16
28°FApr 12Apr 5Apr 1Mar 28Mar 23Mar 18Mar 14Mar 9Mar 2
24°FMar 31Mar 23Mar 17Mar 13Mar 8Mar 3Feb 28Feb 25Feb 18
20°FMar 16Mar 10Mar 5Mar 1Feb 26Feb 22Feb 16Feb 9Feb 1
16°FMar 5Feb 28Feb 23Feb 16Feb 10Feb 4Jan 30Jan 23Jan 10

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 6Oct 13Oct 17Oct 19Oct 22Oct 24Oct 28Nov 1Nov 5
32°FOct 17Oct 22Oct 25Oct 28Oct 31Nov 3Nov 6Nov 10Nov 15
28°FOct 24Oct 30Nov 2Nov 6Nov 9Nov 12Nov 16Nov 21Nov 28
24°FNov 2Nov 7Nov 11Nov 15Nov 19Nov 23Nov 28Dec 2Dec 8
20°FNov 11Nov 17Nov 24Nov 28Dec 2Dec 6Dec 11Dec 18Dec 29
16°FNov 23Dec 1Dec 6Dec 13Dec 19Dec 25Jan 1Jan 7Jan 16

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°F210203197193188184180174167
32°F234224219213208204199193184
28°F257249243238233226219214204
24°F282274267260254249244237225
20°F311302294287282276269261251
16°F345334325317310304297290278

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
3,280
Cooling degree days, base 65°F
2,038
Growing degree days, base 40°F
8,207
Growing degree days, base 45°F
6,681
Growing degree days, base 50°F
5,294
Growing degree days, base 55°F
4,056
Growing degree days, base 60°F
2,971

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January780023
February584254
March39213176
April17948339
May41169594
June1381829
July0533998
August0515979
September17290723
October15478403
November4248138
December709136

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 1.3 km from Sulphur. 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 USC00341745 (Chickasaw Nra). Public domain.