Windsor climate

Windsor Frost Dates and Growing Season

NOAA 1991-2020 normals for Windsor, 0.9 km from Windsor, elevation 877 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Windsor. 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 13 and the first fall freeze around October 22, a growing season of about 191 days.

Median at 36°F
last April 25, first October 13
Median at 32°F
last April 13, first October 22
Median at 28°F
last April 2, 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 8May 4May 1Apr 28Apr 25Apr 22Apr 20Apr 15Apr 11
32°FApr 30Apr 24Apr 21Apr 17Apr 13Apr 10Apr 6Apr 3Mar 30
28°FApr 19Apr 11Apr 7Apr 4Apr 2Mar 31Mar 27Mar 22Mar 17
24°FApr 6Apr 2Mar 29Mar 25Mar 22Mar 19Mar 15Mar 11Mar 6
20°FMar 30Mar 22Mar 19Mar 15Mar 12Mar 9Mar 5Mar 2Feb 25
16°FMar 20Mar 14Mar 10Mar 7Mar 4Mar 1Feb 26Feb 21Feb 13

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 30Oct 4Oct 7Oct 10Oct 13Oct 16Oct 18Oct 21Oct 24
32°FOct 9Oct 14Oct 17Oct 20Oct 22Oct 24Oct 27Oct 30Nov 3
28°FOct 19Oct 24Oct 27Oct 30Nov 1Nov 2Nov 5Nov 9Nov 14
24°FOct 29Nov 1Nov 4Nov 6Nov 9Nov 12Nov 16Nov 21Nov 28
20°FNov 4Nov 8Nov 13Nov 16Nov 21Nov 25Nov 29Dec 2Dec 9
16°FNov 12Nov 19Nov 24Nov 28Dec 1Dec 5Dec 10Dec 15Dec 22

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°F188182177173169166162157151
32°F209204199195191187182178170
28°F232225220215211207203198191
24°F256248243238232228223216210
20°F278270263258254249244239231
16°F299289283278273269263257249

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
5,168
Cooling degree days, base 65°F
1,201
Growing degree days, base 40°F
6,216
Growing degree days, base 45°F
4,934
Growing degree days, base 50°F
3,791
Growing degree days, base 55°F
2,792
Growing degree days, base 60°F
1,929

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12203
February886010
March669463
April35011182
May13287428
June6243687
July1368832
August3327788
September67134518
October31625226
November644249
December97206

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 0.9 km from Windsor. 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 USC00239034 (Windsor). Public domain.