Bridgewater climate

Bridgewater Frost Dates and Growing Season

NOAA 1991-2020 normals for Somerville 4 Nw, 1.6 km from Bridgewater, elevation 134 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Somerville 4 Nw. 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 30 and the first fall freeze around October 20, a growing season of about 172 days.

Median at 36°F
last May 10, first October 9
Median at 32°F
last April 30, first October 20
Median at 28°F
last April 15, first October 31

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 24May 20May 16May 14May 10May 7May 4Apr 30Apr 27
32°FMay 14May 9May 5May 2Apr 30Apr 27Apr 24Apr 20Apr 15
28°FMay 1Apr 26Apr 22Apr 18Apr 15Apr 11Apr 8Apr 5Apr 1
24°FApr 15Apr 8Apr 5Apr 3Apr 1Mar 29Mar 25Mar 21Mar 16
20°FApr 1Mar 29Mar 25Mar 21Mar 18Mar 15Mar 11Mar 7Mar 2
16°FMar 22Mar 17Mar 13Mar 10Mar 7Mar 4Mar 1Feb 26Feb 19

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

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°F171163158155150147143139132
32°F193186180176172168163158151
28°F217210205201198193189184176
24°F245238233228224220215210202
20°F272264258253248244239234227
16°F299292284278274269264257249

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
5,769
Cooling degree days, base 65°F
748
Growing degree days, base 40°F
5,188
Growing degree days, base 45°F
3,996
Growing degree days, base 50°F
2,964
Growing degree days, base 55°F
2,081
Growing degree days, base 60°F
1,340

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,11402
February96901
March825011
April478486
May21931285
June41143552
July2270733
August6214673
September8280450
October3876142
November681028
December96604

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 1.6 km from Bridgewater. 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 USC00288194 (Somerville 4 Nw). Public domain.