Warren County climate

Warren County Frost Dates and Growing Season

NOAA 1991-2020 normals for Arcola, 16.2 km from Warren County, elevation 330 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Arcola. 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 3 and the first fall freeze around November 5, a growing season of about 217 days.

Median at 36°F
last April 16, first October 28
Median at 32°F
last April 3, first November 5
Median at 28°F
last March 23, 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°FMay 2Apr 27Apr 23Apr 20Apr 16Apr 13Apr 9Apr 4Mar 31
32°FApr 19Apr 13Apr 9Apr 6Apr 3Mar 31Mar 28Mar 24Mar 18
28°FApr 7Apr 2Mar 30Mar 27Mar 23Mar 18Mar 15Mar 10Mar 2
24°FMar 27Mar 21Mar 16Mar 13Mar 9Mar 4Feb 28Feb 22Feb 11
20°FMar 15Mar 9Mar 4Feb 28Feb 24Feb 16Feb 7Jan 31Jan 20
16°FMar 5Feb 26Feb 17Feb 6Feb 2Jan 30Jan 24Jan 17Jan 4

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 9Oct 15Oct 20Oct 24Oct 28Nov 1Nov 2Nov 6Nov 11
32°FOct 16Oct 24Oct 29Nov 2Nov 5Nov 8Nov 12Nov 16Nov 23
28°FOct 26Nov 1Nov 6Nov 12Nov 17Nov 21Nov 27Dec 2Dec 9
24°FNov 4Nov 15Nov 23Nov 29Dec 3Dec 9Dec 16Dec 25Jan 2
20°FNov 27Dec 6Dec 13Dec 20Dec 27Jan 1Jan 5Jan 11Jan 20
16°FDec 15Dec 25Dec 31Jan 2Jan 6Jan 11Jan 16Jan 22Feb 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°F217210204199194189184178170
32°F241233226221217212207201192
28°F271259253246240234227221213
24°F306294286278271266259251240
20°F338326316308302296290282271
16°F365361348340333328317307299

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
99% of years
16°F or colder
82% 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
3,342
Cooling degree days, base 65°F
1,462
Growing degree days, base 40°F
7,472
Growing degree days, base 45°F
5,920
Growing degree days, base 50°F
4,539
Growing degree days, base 55°F
3,336
Growing degree days, base 60°F
2,313

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January744027
February595029
March4713107
April20630289
May53117529
June5295739
July0420885
August1365829
September18193626
October18036330
November4263106
December644145

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 16.2 km from Warren 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 USC00310241 (Arcola). Public domain.