Southbridge climate

Southbridge Frost Dates and Growing Season

NOAA 1991-2020 normals for Southbridge 3 Sw, 3.7 km from Southbridge, elevation 685 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Southbridge 3 Sw. 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 25 and the first fall freeze around October 13, a growing season of about 168 days.

Median at 36°F
last May 6, first October 4
Median at 32°F
last April 25, first October 13
Median at 28°F
last April 13, first October 25

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 20May 16May 12May 9May 6May 4May 2Apr 30Apr 27
32°FMay 8May 4May 1Apr 29Apr 25Apr 23Apr 21Apr 18Apr 14
28°FApr 24Apr 20Apr 17Apr 15Apr 13Apr 10Apr 8Apr 6Apr 3
24°FApr 12Apr 8Apr 5Apr 4Apr 2Apr 1Mar 29Mar 25Mar 19
20°FApr 3Mar 31Mar 29Mar 26Mar 23Mar 20Mar 17Mar 14Mar 9
16°FMar 29Mar 24Mar 20Mar 18Mar 15Mar 12Mar 9Mar 5Feb 28

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

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°F163158155152149146143139133
32°F186180176172168165162158152
28°F211205201198193190186182176
24°F237230225221217214209204197
20°F261253249245240235231226219
16°F283275269264260256251246239

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
6,572
Cooling degree days, base 65°F
478
Growing degree days, base 40°F
4,483
Growing degree days, base 45°F
3,382
Growing degree days, base 50°F
2,437
Growing degree days, base 55°F
1,635
Growing degree days, base 60°F
979

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21802
February1,06800
March92503
April564149
May26618231
June6494480
July11174628
August22146589
September14844354
October489184
November749016
December1,04802

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 3.7 km from Southbridge. 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 USC00197627 (Southbridge 3 Sw). Public domain.