Sunapee climate

Sunapee Frost Dates and Growing Season

NOAA 1991-2020 normals for Mt Sunapee, 6.2 km from Sunapee, elevation 1275 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mt Sunapee. 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 2 and the first fall freeze around October 9, a growing season of about 158 days.

Median at 36°F
last May 14, first September 30
Median at 32°F
last May 2, first October 9
Median at 28°F
last April 21, first October 21

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 23May 20May 17May 14May 11May 8May 5May 2
32°FMay 17May 11May 7May 4May 2Apr 30Apr 28Apr 25Apr 21
28°FMay 3Apr 30Apr 26Apr 23Apr 21Apr 18Apr 17Apr 13Apr 9
24°FApr 21Apr 18Apr 15Apr 12Apr 10Apr 7Apr 5Apr 3Mar 31
20°FApr 13Apr 8Apr 5Apr 3Apr 2Mar 31Mar 29Mar 24Mar 18
16°FApr 5Apr 2Mar 31Mar 28Mar 25Mar 22Mar 19Mar 16Mar 11

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 16Sep 21Sep 25Sep 27Sep 30Oct 1Oct 4Oct 7Oct 12
32°FSep 27Oct 1Oct 3Oct 6Oct 9Oct 12Oct 15Oct 19Oct 24
28°FOct 4Oct 9Oct 13Oct 18Oct 21Oct 24Oct 27Oct 30Nov 5
24°FOct 17Oct 25Oct 29Nov 1Nov 3Nov 6Nov 10Nov 13Nov 17
20°FNov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 21Nov 24Nov 30
16°FNov 11Nov 16Nov 20Nov 23Nov 26Nov 29Dec 1Dec 5Dec 10

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°F154148144140137133130125118
32°F176169165162158154151146140
28°F200193189185181178173168163
24°F223217212208204200197192185
20°F245238232228225221217214208
16°F264258253248244240236231224

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
7,459
Cooling degree days, base 65°F
371
Growing degree days, base 40°F
4,072
Growing degree days, base 45°F
3,056
Growing degree days, base 50°F
2,177
Growing degree days, base 55°F
1,426
Growing degree days, base 60°F
818

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,37001
February1,17500
March1,05904
April659032
May31514197
June9572429
July18144590
August35108538
September17832312
October537166
November84008
December1,18001

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 6.2 km from Sunapee. 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 USC00275629 (Mt Sunapee). Public domain.