Pewaukee climate

Pewaukee Frost Dates and Growing Season

NOAA 1991-2020 normals for Waukesha Wwtp, 8.4 km from Pewaukee, elevation 789 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Waukesha Wwtp. 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 May 1 and the first fall freeze around October 13, a growing season of about 162 days.

Median at 36°F
last May 13, first October 2
Median at 32°F
last May 1, first October 13
Median at 28°F
last April 19, first October 23

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 29May 24May 20May 17May 13May 10May 6May 3Apr 29
32°FMay 18May 12May 7May 4May 1Apr 29Apr 26Apr 22Apr 18
28°FMay 5Apr 30Apr 26Apr 22Apr 19Apr 16Apr 13Apr 10Apr 6
24°FApr 21Apr 16Apr 12Apr 10Apr 7Apr 5Apr 3Mar 31Mar 27
20°FApr 11Apr 6Apr 3Apr 1Mar 29Mar 26Mar 23Mar 18Mar 12
16°FApr 2Mar 30Mar 26Mar 22Mar 19Mar 16Mar 12Mar 9Mar 5

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 20Sep 25Sep 28Sep 30Oct 2Oct 5Oct 8Oct 11Oct 15
32°FSep 29Oct 3Oct 7Oct 10Oct 13Oct 16Oct 19Oct 22Oct 25
28°FOct 8Oct 15Oct 18Oct 21Oct 23Oct 26Oct 29Nov 1Nov 6
24°FOct 22Oct 27Oct 30Nov 1Nov 4Nov 6Nov 10Nov 14Nov 18
20°FNov 1Nov 4Nov 7Nov 11Nov 14Nov 16Nov 19Nov 23Nov 27
16°FNov 7Nov 12Nov 16Nov 19Nov 22Nov 25Nov 28Dec 1Dec 6

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°F159154149145141138133129123
32°F183175171167162158155150144
28°F205198193189185181176171164
24°F229222217213210206201195188
20°F249243238234230227222217210
16°F270262256252248244239234227

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
7,247
Cooling degree days, base 65°F
559
Growing degree days, base 40°F
4,513
Growing degree days, base 45°F
3,461
Growing degree days, base 50°F
2,535
Growing degree days, base 55°F
1,739
Growing degree days, base 60°F
1,075

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,40600
February1,17400
March977014
April600256
May28725233
June71116495
July14195646
August22157600
September14857366
October4746112
November851011
December1,22301

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 8.4 km from Pewaukee. 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 USC00478937 (Waukesha Wwtp). Public domain.