Mattoon climate

Mattoon Frost Dates and Growing Season

NOAA 1991-2020 normals for Mattoon, 2 km from Mattoon, elevation 701 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mattoon. 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 11 and the first fall freeze around October 29, a growing season of about 199 days.

Median at 36°F
last April 23, first October 19
Median at 32°F
last April 11, first October 29
Median at 28°F
last April 2, first November 7

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 9May 4Apr 30Apr 26Apr 23Apr 20Apr 18Apr 14Apr 9
32°FApr 28Apr 22Apr 18Apr 15Apr 11Apr 9Apr 6Apr 3Mar 31
28°FApr 17Apr 10Apr 6Apr 4Apr 2Mar 31Mar 27Mar 22Mar 15
24°FApr 6Apr 2Mar 30Mar 26Mar 22Mar 18Mar 15Mar 11Mar 5
20°FMar 29Mar 23Mar 18Mar 15Mar 12Mar 9Mar 5Mar 2Feb 23
16°FMar 19Mar 14Mar 10Mar 6Mar 4Mar 1Feb 25Feb 19Feb 9

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 2Oct 9Oct 13Oct 15Oct 19Oct 21Oct 24Oct 27Oct 30
32°FOct 15Oct 20Oct 24Oct 27Oct 29Oct 31Nov 1Nov 5Nov 9
28°FOct 28Oct 31Nov 2Nov 4Nov 7Nov 10Nov 13Nov 17Nov 21
24°FNov 4Nov 8Nov 11Nov 14Nov 17Nov 20Nov 23Nov 27Dec 2
20°FNov 10Nov 14Nov 18Nov 22Nov 26Nov 30Dec 4Dec 8Dec 15
16°FNov 16Nov 23Nov 28Dec 1Dec 6Dec 10Dec 15Dec 20Dec 25

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°F195188183179175172168164156
32°F217210206202199195190184177
28°F239232227222219215211206200
24°F262253248243239234231227220
20°F283276268264260254249243235
16°F303295287282277272267262253

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
100% 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
5,306
Cooling degree days, base 65°F
1,188
Growing degree days, base 40°F
6,158
Growing degree days, base 45°F
4,912
Growing degree days, base 50°F
3,793
Growing degree days, base 55°F
2,794
Growing degree days, base 60°F
1,919

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,16202
February93804
March711145
April34814176
May11488442
June13261699
July0352817
August3307768
September54141537
October28824247
November670151
December1,00605

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 km from Mattoon. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00115430 (Mattoon). Public domain.