Keys climate

Keys Frost Dates and Growing Season

NOAA 1991-2020 normals for Tahlequah, 15.4 km from Keys, elevation 850 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tahlequah. 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 209 days.

Median at 36°F
last April 15, first October 23
Median at 32°F
last April 4, first October 31
Median at 28°F
last March 23, 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°FMay 4Apr 29Apr 24Apr 19Apr 15Apr 12Apr 8Apr 4Mar 31
32°FApr 24Apr 16Apr 11Apr 7Apr 4Mar 31Mar 28Mar 23Mar 17
28°FApr 9Apr 3Mar 31Mar 27Mar 23Mar 19Mar 15Mar 9Mar 2
24°FMar 31Mar 24Mar 18Mar 14Mar 10Mar 6Mar 2Feb 26Feb 19
20°FMar 20Mar 14Mar 8Mar 4Feb 28Feb 25Feb 19Feb 13Feb 3
16°FMar 13Mar 6Feb 28Feb 23Feb 16Feb 10Feb 3Jan 27Jan 17

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 12Oct 16Oct 19Oct 23Oct 25Oct 28Oct 31Nov 4
32°FOct 16Oct 22Oct 25Oct 29Oct 31Nov 2Nov 6Nov 10Nov 16
28°FOct 26Oct 31Nov 3Nov 7Nov 10Nov 14Nov 18Nov 22Nov 28
24°FNov 3Nov 8Nov 13Nov 18Nov 21Nov 26Nov 30Dec 4Dec 9
20°FNov 12Nov 21Nov 26Nov 30Dec 3Dec 6Dec 10Dec 16Dec 23
16°FNov 24Dec 1Dec 6Dec 12Dec 17Dec 21Dec 26Jan 1Jan 9

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°F211204198193188184179174166
32°F236226219213209204200194186
28°F259250243237232227221214206
24°F282272265260255251244238229
20°F308297289283277271264259250
16°F334323315308301295289281270

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
99% 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
3,312
Cooling degree days, base 65°F
1,863
Growing degree days, base 40°F
8,010
Growing degree days, base 45°F
6,483
Growing degree days, base 50°F
5,106
Growing degree days, base 55°F
3,876
Growing degree days, base 60°F
2,791

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January793124
February596145
March40012172
April16852349
May41152577
June1355804
July0497962
August0459924
September18260691
October15065391
November4318134
December715134

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 15.4 km from Keys. 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 USC00348677 (Tahlequah). Public domain.