Rantoul climate

Rantoul Frost Dates and Growing Season

NOAA 1991-2020 normals for Rantoul, 0.6 km from Rantoul, elevation 740 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rantoul. 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 21 and the first fall freeze around October 18, a growing season of about 179 days.

Median at 36°F
last April 30, first October 8
Median at 32°F
last April 21, first October 18
Median at 28°F
last April 10, first October 29

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 17May 11May 6May 3Apr 30Apr 28Apr 25Apr 21Apr 18
32°FMay 6May 1Apr 27Apr 24Apr 21Apr 18Apr 15Apr 11Apr 7
28°FApr 26Apr 21Apr 17Apr 14Apr 10Apr 7Apr 5Apr 2Mar 30
24°FApr 17Apr 11Apr 6Apr 4Apr 1Mar 30Mar 25Mar 21Mar 15
20°FApr 6Apr 1Mar 28Mar 24Mar 21Mar 17Mar 13Mar 10Mar 4
16°FMar 29Mar 22Mar 18Mar 14Mar 11Mar 8Mar 5Mar 1Feb 23

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°FSep 26Sep 30Oct 3Oct 6Oct 8Oct 11Oct 13Oct 16Oct 20
32°FOct 5Oct 10Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Oct 31
28°FOct 16Oct 20Oct 24Oct 27Oct 29Nov 1Nov 3Nov 6Nov 12
24°FOct 26Oct 31Nov 2Nov 5Nov 7Nov 11Nov 15Nov 18Nov 23
20°FNov 4Nov 8Nov 11Nov 15Nov 19Nov 22Nov 25Nov 29Dec 4
16°FNov 9Nov 15Nov 20Nov 24Nov 28Dec 1Dec 4Dec 9Dec 16

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°F177172168164159156152147139
32°F197191186183179175171165159
28°F220212207203199196191186179
24°F244237231226222217213208201
20°F265258252248243239234226219
16°F287278271265261257251246237

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
5,719
Cooling degree days, base 65°F
1,145
Growing degree days, base 40°F
5,901
Growing degree days, base 45°F
4,697
Growing degree days, base 50°F
3,623
Growing degree days, base 55°F
2,668
Growing degree days, base 60°F
1,840

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,23701
February99103
March766239
April40311148
May14392421
June16265699
July2336800
August5276736
September66141527
October34021206
November695140
December1,05604

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 0.6 km from Rantoul. 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 USW00014806 (Rantoul). Public domain.