Annawan climate

Annawan Frost Dates and Growing Season

NOAA 1991-2020 normals for Kewanee 1 E, 17.2 km from Annawan, elevation 780 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Kewanee 1 E. 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 17, a growing season of about 175 days.

Median at 36°F
last May 4, first October 6
Median at 32°F
last April 24, first October 17
Median at 28°F
last April 13, first October 28

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 18May 13May 9May 6May 4May 1Apr 29Apr 25Apr 21
32°FMay 8May 3Apr 30Apr 28Apr 24Apr 21Apr 18Apr 15Apr 10
28°FApr 29Apr 22Apr 18Apr 15Apr 13Apr 10Apr 7Apr 4Mar 31
24°FApr 18Apr 12Apr 8Apr 5Apr 2Mar 31Mar 27Mar 22Mar 17
20°FApr 8Apr 1Mar 30Mar 26Mar 23Mar 19Mar 16Mar 12Mar 6
16°FMar 29Mar 23Mar 19Mar 16Mar 12Mar 10Mar 6Mar 3Feb 27

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 23Sep 28Oct 1Oct 4Oct 6Oct 9Oct 11Oct 14Oct 19
32°FOct 3Oct 8Oct 12Oct 15Oct 17Oct 20Oct 22Oct 25Oct 29
28°FOct 14Oct 20Oct 23Oct 26Oct 28Oct 30Nov 1Nov 4Nov 9
24°FOct 26Oct 30Nov 1Nov 3Nov 6Nov 9Nov 12Nov 16Nov 20
20°FNov 2Nov 6Nov 10Nov 13Nov 16Nov 19Nov 22Nov 25Nov 30
16°FNov 10Nov 16Nov 20Nov 23Nov 25Nov 28Dec 1Dec 5Dec 11

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°F173167162159155151147142135
32°F195189184179175171167162155
28°F217209205200197193189184176
24°F240233228223219214210205199
20°F262255249244240236231225218
16°F281273267262258254249244237

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
6,407
Cooling degree days, base 65°F
829
Growing degree days, base 40°F
5,262
Growing degree days, base 45°F
4,128
Growing degree days, base 50°F
3,117
Growing degree days, base 55°F
2,224
Growing degree days, base 60°F
1,458

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,33100
February1,08902
March852126
April4776107
May18160355
June24190616
July4269730
August9209665
September10783429
October40211159
November777025
December1,15502

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 17.2 km from Annawan. 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 USC00114710 (Kewanee 1 E). Public domain.