Milwaukee climate

Milwaukee Frost Dates and Growing Season

NOAA 1991-2020 normals for West Allis, 8.1 km from Milwaukee, elevation 723 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for West Allis. 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 26 and the first fall freeze around October 22, a growing season of about 177 days.

Median at 36°F
last May 8, first October 10
Median at 32°F
last April 26, first October 22
Median at 28°F
last April 14, 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 23May 18May 14May 11May 8May 4May 1Apr 27Apr 23
32°FMay 12May 6May 2Apr 29Apr 26Apr 23Apr 20Apr 16Apr 12
28°FApr 30Apr 24Apr 20Apr 16Apr 14Apr 10Apr 7Apr 4Apr 1
24°FApr 15Apr 11Apr 7Apr 4Apr 2Mar 31Mar 28Mar 23Mar 18
20°FApr 5Apr 2Mar 30Mar 27Mar 23Mar 20Mar 16Mar 13Mar 7
16°FMar 28Mar 23Mar 19Mar 16Mar 13Mar 10Mar 7Mar 4Feb 28

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 29Oct 2Oct 5Oct 8Oct 10Oct 13Oct 16Oct 19Oct 24
32°FOct 7Oct 12Oct 16Oct 19Oct 22Oct 25Oct 28Oct 31Nov 3
28°FOct 19Oct 24Oct 28Oct 31Nov 1Nov 4Nov 7Nov 10Nov 14
24°FNov 1Nov 3Nov 6Nov 9Nov 11Nov 14Nov 17Nov 20Nov 25
20°FNov 7Nov 12Nov 15Nov 18Nov 20Nov 23Nov 26Nov 30Dec 5
16°FNov 13Nov 18Nov 22Nov 26Nov 29Dec 1Dec 4Dec 9Dec 15

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°F176169164159156152147143137
32°F197190186181177173169164158
28°F219212207203200195191186178
24°F243236230226223219215210204
20°F262256251247242238234228222
16°F282274269264259255251244238

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
6,585
Cooling degree days, base 65°F
835
Growing degree days, base 40°F
5,078
Growing degree days, base 45°F
3,973
Growing degree days, base 50°F
3,001
Growing degree days, base 55°F
2,154
Growing degree days, base 60°F
1,433

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,30900
February1,10601
March904012
April554474
May23237285
June46166570
July4280741
August7238696
September88100464
October41611143
November784014
December1,13402

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 8.1 km from Milwaukee. 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 USC00479046 (West Allis). Public domain.