Derma climate

Derma Frost Dates and Growing Season

NOAA 1991-2020 normals for Calhoun City, 2.8 km from Derma, elevation 268 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Calhoun City. 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 28 and the first fall freeze around November 5, a growing season of about 223 days.

Median at 36°F
last April 8, first October 27
Median at 32°F
last March 28, first November 5
Median at 28°F
last March 12, first November 17

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 22Apr 17Apr 13Apr 10Apr 8Apr 5Apr 2Mar 30Mar 24
32°FApr 11Apr 6Apr 3Mar 31Mar 28Mar 23Mar 19Mar 14Mar 6
28°FMar 31Mar 25Mar 20Mar 15Mar 12Mar 8Mar 2Feb 27Feb 21
24°FMar 17Mar 11Mar 6Mar 2Feb 27Feb 23Feb 18Feb 11Feb 2
20°FMar 6Mar 1Feb 23Feb 16Feb 11Feb 4Jan 30Jan 24Jan 14
16°FFeb 26Feb 13Feb 5Jan 31Jan 27Jan 22Jan 17Jan 10Jan 2

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 18Oct 22Oct 25Oct 27Oct 30Nov 1Nov 4Nov 8
32°FOct 23Oct 27Oct 31Nov 2Nov 5Nov 7Nov 11Nov 16Nov 22
28°FNov 1Nov 6Nov 10Nov 13Nov 17Nov 21Nov 25Dec 1Dec 5
24°FNov 11Nov 18Nov 23Nov 27Dec 1Dec 5Dec 10Dec 19Dec 28
20°FNov 21Dec 1Dec 6Dec 13Dec 21Dec 27Jan 1Jan 6Jan 15
16°FDec 9Dec 20Dec 27Jan 1Jan 4Jan 7Jan 12Jan 19Jan 30

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°F223215210206201197193190182
32°F248239233228223218213207200
28°F276267261255249243237230222
24°F309299292284278272266260250
20°F343332324317309302296288275
16°F365361353345336331323314302

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
98% of years
16°F or colder
81% 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
2,813
Cooling degree days, base 65°F
2,057
Growing degree days, base 40°F
8,560
Growing degree days, base 45°F
6,963
Growing degree days, base 50°F
5,506
Growing degree days, base 55°F
4,199
Growing degree days, base 60°F
3,048

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January688149
February510476
March33417209
April13366391
May26206645
June1386835
July0498963
August0479944
September8299741
October12488437
November38511151
December605366

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 2.8 km from Derma. 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 USC00221314 (Calhoun City). Public domain.