DeForest climate

DeForest Frost Dates and Growing Season

NOAA 1991-2020 normals for Arlington, 6.3 km from DeForest, elevation 1052 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Arlington. 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 4 and the first fall freeze around October 6, a growing season of about 154 days.

Median at 36°F
last May 14, first September 28
Median at 32°F
last May 4, first October 6
Median at 28°F
last April 22, first October 18

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 25May 21May 18May 14May 11May 8May 4Apr 30
32°FMay 18May 14May 10May 6May 4May 1Apr 28Apr 24Apr 20
28°FMay 7May 2Apr 29Apr 25Apr 22Apr 19Apr 16Apr 12Apr 7
24°FApr 26Apr 20Apr 16Apr 13Apr 10Apr 7Apr 4Apr 1Mar 27
20°FApr 16Apr 9Apr 6Apr 3Apr 1Mar 30Mar 25Mar 22Mar 17
16°FApr 5Apr 1Mar 30Mar 26Mar 23Mar 20Mar 17Mar 14Mar 9

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 15Sep 20Sep 22Sep 25Sep 28Oct 1Oct 2Oct 5Oct 8
32°FSep 23Sep 28Oct 1Oct 4Oct 6Oct 9Oct 12Oct 15Oct 20
28°FOct 3Oct 9Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Oct 31
24°FOct 13Oct 19Oct 23Oct 26Oct 29Nov 1Nov 3Nov 6Nov 12
20°FOct 27Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15Nov 18Nov 23
16°FNov 3Nov 8Nov 12Nov 15Nov 18Nov 21Nov 25Nov 28Dec 4

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°F153147142138135132127122116
32°F172167162158154151146142136
28°F197191186181177173169162156
24°F221214210206202198192187179
20°F244237232227222218214210203
16°F264255250246241237232227220

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
7,457
Cooling degree days, base 65°F
566
Growing degree days, base 40°F
4,515
Growing degree days, base 45°F
3,477
Growing degree days, base 50°F
2,561
Growing degree days, base 55°F
1,767
Growing degree days, base 60°F
1,094

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,47100
February1,22200
March994012
April590260
May26531259
June51124524
July13199651
August26150589
September16254351
October4985103
November888011
December1,27701

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 6.3 km from DeForest. 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 USC00470308 (Arlington). Public domain.