South Windham climate

South Windham Frost Dates and Growing Season

NOAA 1991-2020 normals for Willimantic Windham AP, 7 km from South Windham, elevation 247 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Willimantic Windham AP. 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 28 and the first fall freeze around October 13, a growing season of about 167 days.

Median at 36°F
last May 9, first October 3
Median at 32°F
last April 28, first October 13
Median at 28°F
last April 14, first October 25

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 22May 18May 14May 11May 9May 6May 3Apr 30Apr 27
32°FMay 11May 7May 3Apr 30Apr 28Apr 26Apr 23Apr 20Apr 17
28°FApr 29Apr 24Apr 20Apr 17Apr 14Apr 12Apr 9Apr 5Apr 2
24°FApr 15Apr 9Apr 5Apr 3Apr 2Mar 31Mar 28Mar 24Mar 17
20°FApr 3Mar 31Mar 28Mar 25Mar 21Mar 18Mar 15Mar 12Mar 7
16°FMar 27Mar 22Mar 19Mar 16Mar 13Mar 10Mar 7Mar 3Feb 26

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 23Sep 27Sep 29Oct 1Oct 3Oct 5Oct 8Oct 12Oct 16
32°FOct 2Oct 5Oct 8Oct 10Oct 13Oct 16Oct 19Oct 24Oct 29
28°FOct 10Oct 15Oct 19Oct 23Oct 25Oct 29Nov 1Nov 4Nov 7
24°FOct 21Oct 26Oct 31Nov 2Nov 5Nov 8Nov 12Nov 15Nov 22
20°FNov 1Nov 8Nov 12Nov 15Nov 19Nov 22Nov 25Nov 30Dec 5
16°FNov 16Nov 21Nov 25Nov 29Dec 1Dec 4Dec 8Dec 13Dec 21

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°F164158154150146143140136129
32°F189180175171167164160155149
28°F213206202197193188184179170
24°F237231226221217213208203196
20°F264257252247242238233227220
16°F287280273268263259255250241

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
6,094
Cooling degree days, base 65°F
626
Growing degree days, base 40°F
4,916
Growing degree days, base 45°F
3,758
Growing degree days, base 50°F
2,758
Growing degree days, base 55°F
1,902
Growing degree days, base 60°F
1,187

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,17300
February1,00501
March868011
April515469
May22724273
June50110510
July4232693
August11186640
September11363403
October4166131
November705023
December1,00603

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 7 km from South Windham. 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 USW00054767 (Willimantic Windham AP). Public domain.