Champaign County climate

Champaign County Frost Dates and Growing Season

NOAA 1991-2020 normals for Urbana Wwtp, 4.5 km from Champaign County, elevation 1019 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Urbana Wwtp. 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 24 and the first fall freeze around October 19, a growing season of about 179 days.

Median at 36°F
last May 4, first October 9
Median at 32°F
last April 24, first October 19
Median at 28°F
last April 12, first November 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°FMay 20May 14May 10May 7May 4May 1Apr 29Apr 26Apr 20
32°FMay 10May 4Apr 30Apr 27Apr 24Apr 21Apr 18Apr 15Apr 10
28°FApr 29Apr 22Apr 18Apr 15Apr 12Apr 9Apr 6Apr 2Mar 28
24°FApr 15Apr 10Apr 6Apr 3Apr 1Mar 30Mar 25Mar 20Mar 16
20°FApr 5Apr 1Mar 29Mar 23Mar 20Mar 17Mar 14Mar 10Mar 4
16°FMar 27Mar 21Mar 17Mar 14Mar 10Mar 7Mar 3Feb 28Feb 21

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 28Oct 1Oct 3Oct 6Oct 9Oct 11Oct 14Oct 17Oct 22
32°FOct 7Oct 11Oct 14Oct 17Oct 19Oct 22Oct 26Oct 29Nov 2
28°FOct 18Oct 22Oct 26Oct 30Nov 1Nov 2Nov 5Nov 9Nov 15
24°FOct 31Nov 3Nov 6Nov 9Nov 12Nov 15Nov 19Nov 23Nov 30
20°FNov 8Nov 13Nov 17Nov 21Nov 25Nov 29Dec 2Dec 7Dec 15
16°FNov 16Nov 23Nov 29Dec 1Dec 6Dec 10Dec 15Dec 19Dec 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°F176170165162158154150145137
32°F197192187183179175171165158
28°F220214209205201198194188182
24°F246239234230225221216212205
20°F273265259253249244239233226
16°F296287281276272267261254248

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
5,839
Cooling degree days, base 65°F
845
Growing degree days, base 40°F
5,413
Growing degree days, base 45°F
4,223
Growing degree days, base 50°F
3,173
Growing degree days, base 55°F
2,257
Growing degree days, base 60°F
1,480

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,17202
February98703
March810130
April4496122
May18358352
June31188607
July3268730
August7221679
September9292452
October38311160
November699031
December1,02304

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 4.5 km from Champaign 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 USC00338552 (Urbana Wwtp). Public domain.