Storrs climate

Storrs Frost Dates and Growing Season

NOAA 1991-2020 normals for Storrs, 2.2 km from Storrs, elevation 665 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Storrs. 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 19 and the first fall freeze around October 22, a growing season of about 186 days.

Median at 36°F
last May 3, first October 10
Median at 32°F
last April 19, first October 22
Median at 28°F
last April 6, first November 4

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 16May 11May 8May 5May 3Apr 30Apr 28Apr 24Apr 20
32°FMay 3Apr 29Apr 25Apr 22Apr 19Apr 17Apr 14Apr 11Apr 7
28°FApr 19Apr 14Apr 11Apr 8Apr 6Apr 4Apr 2Mar 31Mar 26
24°FApr 8Apr 4Apr 3Apr 1Mar 30Mar 27Mar 23Mar 20Mar 15
20°FApr 1Mar 30Mar 25Mar 22Mar 19Mar 16Mar 13Mar 9Mar 5
16°FMar 26Mar 21Mar 17Mar 14Mar 11Mar 8Mar 5Mar 2Feb 24

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

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°F180172168163160157153148142
32°F205199193189186182178172165
28°F230223219214211206202196189
24°F254247242237233228223219212
20°F277269263258253249244239232
16°F298289284278272268263257249

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
6,141
Cooling degree days, base 65°F
569
Growing degree days, base 40°F
4,847
Growing degree days, base 45°F
3,688
Growing degree days, base 50°F
2,683
Growing degree days, base 55°F
1,825
Growing degree days, base 60°F
1,118

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18100
February1,01401
March890010
April529471
May24921252
June6099490
July6212671
August13168620
September11062404
October4044133
November686028
December1,00104

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 2.2 km from Storrs. 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 USC00068138 (Storrs). Public domain.