Windsor climate

Windsor Frost Dates and Growing Season

NOAA 1991-2020 normals for Williamston 1 E, 18 km from Windsor, elevation 20 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Williamston 1 E. 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 March 20 and the first fall freeze around November 12, a growing season of about 239 days.

Median at 36°F
last April 2, first November 1
Median at 32°F
last March 20, first November 12
Median at 28°F
last March 5, first November 26

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°FApr 17Apr 12Apr 8Apr 5Apr 2Mar 31Mar 28Mar 23Mar 17
32°FApr 5Mar 31Mar 28Mar 24Mar 20Mar 17Mar 13Mar 7Mar 1
28°FMar 25Mar 18Mar 14Mar 10Mar 5Mar 1Feb 24Feb 16Feb 7
24°FMar 11Mar 5Feb 28Feb 22Feb 16Feb 9Feb 4Jan 30Jan 19
20°FFeb 26Feb 14Feb 6Feb 1Jan 30Jan 24Jan 18Jan 13Jan 4
16°FFeb 8Feb 1Jan 31Jan 26Jan 21Jan 18Jan 14Jan 10Jan 3

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 21Oct 25Oct 29Oct 31Nov 1Nov 4Nov 6Nov 10Nov 16
32°FOct 31Nov 3Nov 6Nov 9Nov 12Nov 15Nov 19Nov 25Dec 4
28°FNov 7Nov 12Nov 17Nov 22Nov 26Dec 1Dec 5Dec 13Dec 25
24°FNov 24Dec 1Dec 5Dec 11Dec 19Dec 28Jan 2Jan 9Jan 18
20°FDec 8Dec 18Dec 28Jan 1Jan 6Jan 10Jan 15Jan 20Jan 31
16°FDec 30Jan 3Jan 7Jan 12Jan 15Jan 18Jan 22Jan 28Feb 1

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°F236227222218214209206201195
32°F268257250245239234229223215
28°F302289282275268261256249238
24°F337326317309304300292282271
20°F365363352345337333326317306
16°F365365365365365359349341333

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
98% of years
20°F or colder
80% of years
16°F or colder
45% 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
3,033
Cooling degree days, base 65°F
1,769
Growing degree days, base 40°F
8,054
Growing degree days, base 45°F
6,473
Growing degree days, base 50°F
5,048
Growing degree days, base 55°F
3,788
Growing degree days, base 60°F
2,696

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January700140
February557252
March4179149
April18052335
May50158574
June3342789
July0463928
August0415880
September10252691
October13963395
November3798151
December598363

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 18 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 USC00319440 (Williamston 1 E). Public domain.