Windham County climate

Windham County Frost Dates and Growing Season

NOAA 1991-2020 normals for Walpole 2S Nepp, 23.4 km from Windham County, elevation 604 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Walpole 2S Nepp. 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 8 and the first fall freeze around October 3, a growing season of about 149 days.

Median at 36°F
last May 21, first September 25
Median at 32°F
last May 8, first October 3
Median at 28°F
last April 25, first October 16

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°FJun 6Jun 1May 28May 25May 21May 18May 15May 11May 6
32°FMay 22May 18May 14May 11May 8May 4May 1Apr 29Apr 24
28°FMay 11May 4May 1Apr 28Apr 25Apr 22Apr 19Apr 15Apr 10
24°FApr 23Apr 19Apr 16Apr 12Apr 9Apr 7Apr 5Apr 2Mar 30
20°FApr 11Apr 6Apr 4Apr 2Mar 31Mar 29Mar 26Mar 22Mar 16
16°FApr 3Mar 31Mar 29Mar 24Mar 21Mar 18Mar 15Mar 13Mar 8

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 12Sep 16Sep 19Sep 22Sep 25Sep 27Sep 30Oct 2Oct 6
32°FSep 22Sep 27Sep 30Oct 1Oct 3Oct 5Oct 9Oct 14Oct 20
28°FOct 1Oct 5Oct 8Oct 12Oct 16Oct 20Oct 25Oct 31Nov 3
24°FOct 11Oct 17Oct 22Oct 27Oct 30Nov 1Nov 5Nov 9Nov 14
20°FOct 25Nov 1Nov 4Nov 8Nov 12Nov 16Nov 19Nov 23Nov 27
16°FNov 8Nov 13Nov 18Nov 21Nov 24Nov 27Dec 1Dec 4Dec 9

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°F146138133130125122118112105
32°F170163158153149145141136129
28°F198190184180175170166161153
24°F223215210206202198193187180
20°F245238233229226221217212205
16°F267261256251247243238232225

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
7,259
Cooling degree days, base 65°F
383
Growing degree days, base 40°F
4,140
Growing degree days, base 45°F
3,113
Growing degree days, base 50°F
2,218
Growing degree days, base 55°F
1,474
Growing degree days, base 60°F
856

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,34200
February1,16600
March1,02700
April617136
May31212193
June8766430
July14151602
August25113553
September17840321
October511274
November825010
December1,15600

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 23.4 km from Windham County. 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 USC00278856 (Walpole 2S Nepp). Public domain.