Lyme climate

Lyme Frost Dates and Growing Season

NOAA 1991-2020 normals for Union Village Dam, 8.4 km from Lyme, elevation 460 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Union Village Dam. 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 9 and the first fall freeze around October 2, a growing season of about 145 days.

Median at 36°F
last May 21, first September 24
Median at 32°F
last May 9, first October 2
Median at 28°F
last April 30, first October 12

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 4May 30May 27May 24May 21May 19May 16May 12May 8
32°FMay 22May 18May 14May 11May 9May 7May 4May 2Apr 29
28°FMay 10May 7May 4May 1Apr 30Apr 28Apr 25Apr 23Apr 19
24°FApr 29Apr 25Apr 22Apr 20Apr 18Apr 15Apr 12Apr 9Apr 6
20°FApr 19Apr 15Apr 12Apr 10Apr 8Apr 6Apr 4Apr 2Mar 30
16°FApr 10Apr 7Apr 5Apr 3Apr 1Mar 31Mar 28Mar 23Mar 18

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 10Sep 15Sep 18Sep 21Sep 24Sep 26Sep 28Oct 1Oct 4
32°FSep 20Sep 25Sep 28Sep 30Oct 2Oct 4Oct 6Oct 9Oct 15
28°FSep 30Oct 3Oct 6Oct 9Oct 12Oct 15Oct 18Oct 22Oct 27
24°FOct 8Oct 14Oct 17Oct 20Oct 24Oct 28Nov 1Nov 3Nov 7
20°FOct 20Oct 26Oct 31Nov 2Nov 4Nov 7Nov 10Nov 14Nov 18
16°FNov 2Nov 7Nov 11Nov 14Nov 16Nov 18Nov 21Nov 24Nov 29

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°F140135131128124120116112106
32°F161155151148145141138133127
28°F184177173169165162158154148
24°F207202197192189185180175168
20°F228222217213209205201196190
16°F245240235231228224220216210

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
7,847
Cooling degree days, base 65°F
393
Growing degree days, base 40°F
4,019
Growing degree days, base 45°F
3,039
Growing degree days, base 50°F
2,186
Growing degree days, base 55°F
1,452
Growing degree days, base 60°F
843

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46700
February1,26500
March1,10306
April683130
May32111196
June9067430
July17153601
August33120552
September19640305
October554163
November87905
December1,23700

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 8.4 km from Lyme. 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 USC00438556 (Union Village Dam). Public domain.