Simpson County climate

Simpson County Frost Dates and Growing Season

NOAA 1991-2020 normals for D'lo 2 Sw, 4.8 km from Simpson County, elevation 334 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for D'lo 2 Sw. 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 10 and the first fall freeze around November 16, a growing season of about 252 days.

Median at 36°F
last March 27, first November 3
Median at 32°F
last March 10, first November 16
Median at 28°F
last February 23, first December 1

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 12Apr 6Apr 3Mar 31Mar 27Mar 22Mar 18Mar 12Mar 3
32°FApr 1Mar 25Mar 19Mar 15Mar 10Mar 5Mar 1Feb 25Feb 17
28°FMar 16Mar 9Mar 3Feb 28Feb 23Feb 17Feb 9Feb 3Jan 26
24°FMar 4Feb 25Feb 14Feb 6Feb 1Jan 28Jan 21Jan 13Dec 31
20°FFeb 12Feb 4Jan 31Jan 27Jan 21Jan 16Jan 9Jan 2Dec 25
16°FFeb 5Jan 31Jan 27Jan 24Jan 17Jan 13Jan 9Jan 5Dec 31

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 20Oct 25Oct 29Nov 1Nov 3Nov 6Nov 10Nov 15Nov 23
32°FOct 31Nov 4Nov 8Nov 12Nov 16Nov 20Nov 25Dec 1Dec 7
28°FNov 10Nov 16Nov 21Nov 27Dec 1Dec 5Dec 13Dec 26Jan 5
24°FNov 21Dec 1Dec 6Dec 15Dec 26Jan 1Jan 7Jan 13Jan 26
20°FDec 5Dec 18Dec 29Jan 1Jan 6Jan 10Jan 15Jan 22Feb 2
16°FDec 24Jan 1Jan 2Jan 7Jan 11Jan 16Jan 21Jan 25Feb 2

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°F247238232226221217212206199
32°F284273264258252246240233224
28°F327311301294287278271262253
24°F365348337331322314305297285
20°F365365365365360350339332320
16°F365365365365365365365362343

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
91% of years
20°F or colder
57% of years
16°F or colder
22% 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
1,888
Cooling degree days, base 65°F
2,826
Growing degree days, base 40°F
10,119
Growing degree days, base 45°F
8,394
Growing degree days, base 50°F
6,780
Growing degree days, base 55°F
5,307
Growing degree days, base 60°F
3,986

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January48910123
February34515158
March20455338
April75128505
May9317773
June0504954
July05941,059
August05771,041
September2413861
October68164564
November25833258
December43918149

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 4.8 km from Simpson County. 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 USC00222385 (D'lo 2 Sw). Public domain.