Winnebago climate

Winnebago Frost Dates and Growing Season

NOAA 1991-2020 normals for Rockford Gtr Rockford AP, 14.6 km from Winnebago, elevation 730 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rockford Gtr Rockford 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 24 and the first fall freeze around October 17, a growing season of about 174 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 19May 14May 10May 7May 4May 2Apr 29Apr 26Apr 21
32°FMay 8May 2Apr 30Apr 27Apr 24Apr 21Apr 18Apr 15Apr 10
28°FApr 27Apr 22Apr 19Apr 16Apr 13Apr 9Apr 7Apr 3Mar 31
24°FApr 18Apr 11Apr 7Apr 4Apr 2Mar 31Mar 28Mar 23Mar 16
20°FApr 5Apr 1Mar 29Mar 25Mar 21Mar 18Mar 15Mar 12Mar 6
16°FMar 28Mar 22Mar 19Mar 16Mar 13Mar 10Mar 7Mar 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 28Sep 30Oct 3Oct 6Oct 9Oct 12Oct 15Oct 20
32°FOct 2Oct 8Oct 12Oct 14Oct 17Oct 19Oct 22Oct 26Oct 30
28°FOct 14Oct 20Oct 23Oct 26Oct 28Oct 30Nov 1Nov 5Nov 10
24°FOct 26Oct 30Nov 1Nov 4Nov 6Nov 10Nov 13Nov 18Nov 23
20°FNov 4Nov 8Nov 12Nov 15Nov 19Nov 21Nov 25Nov 28Dec 2
16°FNov 10Nov 16Nov 20Nov 23Nov 26Nov 29Dec 2Dec 6Dec 12

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°F173166161158153149144140134
32°F192187182178174170166160154
28°F217210206201197193189185177
24°F241233228224219216212207200
20°F262256251246241236232228221
16°F281272267263259255251245238

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
6,497
Cooling degree days, base 65°F
838
Growing degree days, base 40°F
5,209
Growing degree days, base 45°F
4,084
Growing degree days, base 50°F
3,083
Growing degree days, base 55°F
2,207
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
January1,33900
February1,10301
March860224
April482597
May19954333
June27182604
July3274736
August8222679
September10789436
October41211150
November786021
December1,17002

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 14.6 km from Winnebago. 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 USW00094822 (Rockford Gtr Rockford AP). Public domain.