Geneva climate

Geneva Frost Dates and Growing Season

NOAA 1991-2020 normals for West Chicago Dupage AP, 5.7 km from Geneva, elevation 754 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for West Chicago Dupage AP. 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 25 and the first fall freeze around October 19, a growing season of about 174 days.

Median at 36°F
last May 6, first October 7
Median at 32°F
last April 25, first October 19
Median at 28°F
last April 14, 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 24May 18May 14May 10May 6May 3Apr 30Apr 27Apr 23
32°FMay 12May 5May 1Apr 28Apr 25Apr 23Apr 19Apr 16Apr 11
28°FApr 29Apr 24Apr 20Apr 17Apr 14Apr 11Apr 8Apr 4Mar 31
24°FApr 18Apr 12Apr 8Apr 4Apr 2Mar 31Mar 28Mar 23Mar 17
20°FApr 4Mar 31Mar 28Mar 24Mar 20Mar 17Mar 14Mar 11Mar 5
16°FMar 27Mar 21Mar 17Mar 14Mar 12Mar 9Mar 6Mar 1Feb 25

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 25Sep 29Oct 2Oct 5Oct 7Oct 10Oct 13Oct 16Oct 20
32°FOct 5Oct 10Oct 14Oct 16Oct 19Oct 21Oct 24Oct 26Oct 30
28°FOct 16Oct 21Oct 24Oct 26Oct 29Nov 1Nov 4Nov 7Nov 12
24°FOct 28Nov 1Nov 4Nov 7Nov 9Nov 13Nov 17Nov 21Nov 25
20°FNov 6Nov 10Nov 14Nov 18Nov 21Nov 24Nov 28Dec 1Dec 5
16°FNov 13Nov 19Nov 23Nov 26Nov 30Dec 2Dec 5Dec 11Dec 17

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°F173167162158153149145140133
32°F194187183178174170166161153
28°F216210204200197193188183176
24°F243234230224221217213209201
20°F265258253248244239234229221
16°F285277271266262257253247240

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
6,364
Cooling degree days, base 65°F
822
Growing degree days, base 40°F
5,199
Growing degree days, base 45°F
4,063
Growing degree days, base 50°F
3,059
Growing degree days, base 55°F
2,181
Growing degree days, base 60°F
1,434

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,29300
February1,06502
March850226
April492594
May21150318
June33175593
July4272733
August7221679
September10088440
October40711151
November768021
December1,13502

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 5.7 km from Geneva. 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 USW00094892 (West Chicago Dupage AP). Public domain.