Tulsa County climate

Tulsa County Frost Dates and Growing Season

NOAA 1991-2020 normals for Tulsa Intl AP, 10 km from Tulsa County, elevation 650 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tulsa Intl AP. 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 31 and the first fall freeze around November 4, a growing season of about 220 days.

Median at 36°F
last April 10, first October 26
Median at 32°F
last March 31, first November 4
Median at 28°F
last March 17, first November 13

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 27Apr 21Apr 18Apr 14Apr 10Apr 7Apr 4Mar 31Mar 26
32°FApr 15Apr 9Apr 5Apr 2Mar 31Mar 27Mar 23Mar 18Mar 11
28°FApr 5Mar 31Mar 26Mar 22Mar 17Mar 13Mar 9Mar 4Feb 28
24°FMar 23Mar 16Mar 12Mar 9Mar 5Mar 1Feb 27Feb 23Feb 17
20°FMar 12Mar 7Mar 3Feb 28Feb 25Feb 20Feb 16Feb 11Jan 31
16°FMar 6Feb 28Feb 23Feb 17Feb 12Feb 5Jan 31Jan 26Jan 16

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 11Oct 17Oct 21Oct 23Oct 26Oct 29Oct 31Nov 3Nov 6
32°FOct 20Oct 26Oct 30Nov 1Nov 4Nov 6Nov 9Nov 12Nov 19
28°FOct 31Nov 3Nov 6Nov 10Nov 13Nov 16Nov 21Nov 25Dec 1
24°FNov 6Nov 11Nov 16Nov 21Nov 25Nov 29Dec 2Dec 6Dec 12
20°FNov 17Nov 24Nov 29Dec 3Dec 7Dec 12Dec 18Dec 24Jan 2
16°FNov 30Dec 8Dec 14Dec 20Dec 25Dec 31Jan 4Jan 11Jan 18

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°F221213207202198194190184176
32°F243235229225220215210205198
28°F268258252247242238233227217
24°F290282276270265260255249241
20°F318306300294288284277269260
16°F345334327319313307301293283

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
3,451
Cooling degree days, base 65°F
2,128
Growing degree days, base 40°F
8,196
Growing degree days, base 45°F
6,690
Growing degree days, base 50°F
5,332
Growing degree days, base 55°F
4,118
Growing degree days, base 60°F
3,049

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January823120
February622246
March41815165
April17953340
May41183608
June1407856
July05691,034
August05351,000
September17281714
October16074393
November4468127
December744130

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 10 km from Tulsa County. 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 USW00013968 (Tulsa Intl AP). Public domain.