Wethersfield climate

Wethersfield Frost Dates and Growing Season

NOAA 1991-2020 normals for Hartford Brainard Fld, 2.5 km from Wethersfield, elevation 19 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hartford Brainard Fld. 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 17 and the first fall freeze around October 26, a growing season of about 191 days.

Median at 36°F
last April 30, first October 14
Median at 32°F
last April 17, first October 26
Median at 28°F
last April 3, first November 5

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 14May 9May 5May 2Apr 30Apr 27Apr 24Apr 20Apr 17
32°FMay 1Apr 27Apr 23Apr 20Apr 17Apr 14Apr 11Apr 6Apr 1
28°FApr 21Apr 15Apr 10Apr 6Apr 3Apr 1Mar 30Mar 27Mar 21
24°FApr 6Apr 1Mar 30Mar 27Mar 24Mar 20Mar 16Mar 13Mar 8
20°FMar 30Mar 25Mar 21Mar 17Mar 14Mar 11Mar 8Mar 5Feb 28
16°FMar 22Mar 17Mar 12Mar 8Mar 5Mar 2Feb 28Feb 23Feb 15

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

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°F186180175171167163159154148
32°F212205199195191187182177169
28°F237231224220216211205200193
24°F260253247243238233228222215
20°F283276270264260256251246238
16°F305298291286281277272268260

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
5,620
Cooling degree days, base 65°F
914
Growing degree days, base 40°F
5,500
Growing degree days, base 45°F
4,293
Growing degree days, base 50°F
3,238
Growing degree days, base 55°F
2,323
Growing degree days, base 60°F
1,546

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,13002
February95801
March819015
April4556101
May18344332
June27168591
July1316780
August3270732
September76100475
October35110173
November650034
December96704

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 2.5 km from Wethersfield. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00014752 (Hartford Brainard Fld). Public domain.