De Kalb climate

De Kalb Frost Dates and Growing Season

NOAA 1991-2020 normals for Dekalb, 3.3 km from De Kalb, elevation 341 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dekalb. 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 26 and the first fall freeze around November 6, a growing season of about 225 days.

Median at 36°F
last April 7, first October 29
Median at 32°F
last March 26, first November 6
Median at 28°F
last March 11, first November 16

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 24Apr 19Apr 15Apr 10Apr 7Apr 4Mar 31Mar 27Mar 20
32°FApr 14Apr 6Apr 2Mar 30Mar 26Mar 22Mar 17Mar 13Mar 6
28°FMar 31Mar 23Mar 19Mar 15Mar 11Mar 7Mar 3Feb 28Feb 21
24°FMar 17Mar 11Mar 6Mar 3Feb 28Feb 23Feb 17Feb 9Jan 31
20°FMar 6Feb 28Feb 21Feb 14Feb 7Jan 31Jan 27Jan 17Jan 7
16°FFeb 25Feb 12Feb 3Jan 29Jan 23Jan 16Jan 10Jan 4Dec 25

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 14Oct 19Oct 23Oct 26Oct 29Nov 1Nov 3Nov 7Nov 12
32°FOct 22Oct 28Nov 1Nov 3Nov 6Nov 9Nov 13Nov 17Nov 24
28°FOct 31Nov 5Nov 8Nov 12Nov 16Nov 21Nov 26Dec 1Dec 6
24°FNov 9Nov 15Nov 20Nov 25Nov 30Dec 4Dec 9Dec 17Dec 25
20°FNov 21Nov 30Dec 5Dec 11Dec 19Dec 25Dec 30Jan 5Jan 16
16°FDec 5Dec 13Dec 24Dec 30Jan 2Jan 7Jan 12Jan 19Feb 1

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°F227218213208203199194190182
32°F249242236230225221216210202
28°F276268261256250246241234224
24°F314303293285279273266259249
20°F347336329320313306298289276
16°F365365363354346338331320306

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
96% of years
16°F or colder
71% 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
2,767
Cooling degree days, base 65°F
2,115
Growing degree days, base 40°F
8,653
Growing degree days, base 45°F
7,044
Growing degree days, base 50°F
5,574
Growing degree days, base 55°F
4,262
Growing degree days, base 60°F
3,105

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January665145
February512267
March33716205
April13259382
May23209651
June0383832
July0519984
August0508973
September9315756
October11586442
November36313172
December610465

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 3.3 km from De Kalb. 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 USC00412352 (Dekalb). Public domain.