Ledyard climate

Ledyard Frost Dates and Growing Season

NOAA 1991-2020 normals for Groton, 10.2 km from Ledyard, elevation 40 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Groton. 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 8 and the first fall freeze around November 2, a growing season of about 207 days.

Median at 36°F
last April 22, first October 21
Median at 32°F
last April 8, first November 2
Median at 28°F
last March 29, first November 14

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 5May 1Apr 29Apr 25Apr 22Apr 20Apr 17Apr 14Apr 10
32°FApr 22Apr 17Apr 14Apr 11Apr 8Apr 5Apr 3Apr 1Mar 28
28°FApr 7Apr 4Apr 2Mar 31Mar 29Mar 26Mar 23Mar 18Mar 14
24°FMar 31Mar 27Mar 23Mar 20Mar 17Mar 15Mar 12Mar 9Mar 4
20°FMar 24Mar 19Mar 15Mar 12Mar 10Mar 7Mar 4Feb 28Feb 22
16°FMar 16Mar 10Mar 7Mar 4Mar 1Feb 26Feb 22Feb 15Feb 7

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 8Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Oct 31Nov 4
32°FOct 18Oct 23Oct 27Oct 31Nov 2Nov 4Nov 7Nov 11Nov 15
28°FNov 1Nov 4Nov 9Nov 12Nov 14Nov 17Nov 21Nov 25Dec 1
24°FNov 13Nov 18Nov 22Nov 26Nov 29Dec 1Dec 4Dec 8Dec 14
20°FNov 25Nov 30Dec 3Dec 6Dec 10Dec 14Dec 19Dec 23Dec 28
16°FDec 5Dec 12Dec 17Dec 21Dec 24Dec 28Jan 1Jan 6Jan 13

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°F199193189185181178174169162
32°F226220216211207203200195188
28°F255247242237232228223218212
24°F277269265260256251247243236
20°F299292286282277273268262255
16°F321311306302297293289284275

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
5,333
Cooling degree days, base 65°F
721
Growing degree days, base 40°F
5,339
Growing degree days, base 45°F
4,078
Growing degree days, base 50°F
2,990
Growing degree days, base 55°F
2,072
Growing degree days, base 60°F
1,319

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,04502
February90001
March79209
April484166
May22714258
June43110518
July2261724
August3234696
September6791475
October31410192
November584044
December87407

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 10.2 km from Ledyard. 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 USC00063207 (Groton). Public domain.