Winthrop Harbor climate

Winthrop Harbor Frost Dates and Growing Season

NOAA 1991-2020 normals for Kenosha, 9.1 km from Winthrop Harbor, elevation 600 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Kenosha. 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 19 and the first fall freeze around October 26, a growing season of about 189 days.

Median at 36°F
last May 1, first October 17
Median at 32°F
last April 19, first October 26
Median at 28°F
last April 8, first November 6

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 16May 11May 7May 4May 1Apr 29Apr 26Apr 22Apr 17
32°FMay 3Apr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 11Apr 6
28°FApr 21Apr 17Apr 12Apr 10Apr 8Apr 5Apr 3Mar 31Mar 26
24°FApr 11Apr 6Apr 3Apr 1Mar 29Mar 26Mar 22Mar 18Mar 12
20°FApr 3Mar 30Mar 26Mar 21Mar 17Mar 14Mar 11Mar 7Mar 3
16°FMar 27Mar 20Mar 16Mar 13Mar 9Mar 6Mar 3Feb 28Feb 22

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°FOct 1Oct 7Oct 10Oct 14Oct 17Oct 19Oct 22Oct 25Oct 29
32°FOct 11Oct 18Oct 21Oct 24Oct 26Oct 29Nov 1Nov 4Nov 9
28°FOct 24Oct 28Nov 1Nov 3Nov 6Nov 9Nov 12Nov 15Nov 20
24°FNov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 21Nov 25Nov 29
20°FNov 8Nov 13Nov 17Nov 21Nov 24Nov 26Nov 30Dec 3Dec 9
16°FNov 16Nov 21Nov 26Nov 29Dec 1Dec 4Dec 8Dec 13Dec 19

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°F185179174170167163159154147
32°F208201197193189186182177170
28°F231223218214210206202196190
24°F253246239235232227222218212
20°F274266260254250246240236228
16°F290282276272267262257252244

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
6,617
Cooling degree days, base 65°F
609
Growing degree days, base 40°F
4,686
Growing degree days, base 45°F
3,581
Growing degree days, base 50°F
2,633
Growing degree days, base 55°F
1,818
Growing degree days, base 60°F
1,142

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27200
February1,06101
March906011
April600246
May32116195
June8992454
July9223679
August9200656
September10171422
October3976146
November747023
December1,10501

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 9.1 km from Winthrop Harbor. 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 USC00474174 (Kenosha). Public domain.