Weston climate

Weston Frost Dates and Growing Season

NOAA 1991-2020 normals for Natick, 10 km from Weston, elevation 180 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Natick. 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 26 and the first fall freeze around October 12, a growing season of about 169 days.

Median at 36°F
last May 7, first October 4
Median at 32°F
last April 26, first October 12
Median at 28°F
last April 13, first October 24

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 19May 15May 12May 10May 7May 4May 2Apr 30Apr 26
32°FMay 9May 4May 1Apr 29Apr 26Apr 23Apr 21Apr 18Apr 14
28°FApr 24Apr 20Apr 18Apr 15Apr 13Apr 10Apr 8Apr 5Apr 2
24°FApr 14Apr 8Apr 5Apr 3Apr 2Mar 31Mar 30Mar 25Mar 20
20°FApr 3Mar 31Mar 30Mar 27Mar 24Mar 21Mar 18Mar 15Mar 10
16°FMar 29Mar 24Mar 21Mar 18Mar 15Mar 13Mar 9Mar 6Mar 1

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 26Sep 29Oct 1Oct 2Oct 4Oct 6Oct 9Oct 12Oct 15
32°FOct 1Oct 4Oct 6Oct 9Oct 12Oct 15Oct 18Oct 21Oct 26
28°FOct 10Oct 14Oct 18Oct 20Oct 24Oct 27Oct 29Nov 2Nov 6
24°FOct 20Oct 25Oct 29Nov 1Nov 3Nov 6Nov 10Nov 13Nov 20
20°FNov 1Nov 5Nov 9Nov 13Nov 16Nov 20Nov 23Nov 29Dec 4
16°FNov 15Nov 20Nov 24Nov 27Dec 1Dec 3Dec 7Dec 11Dec 18

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°F162158155152149146143138133
32°F186179175171169165161157152
28°F210204199195192189185180174
24°F234227222218215211207203196
20°F259252247243238233229224218
16°F280273268264260255250246238

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
6,380
Cooling degree days, base 65°F
556
Growing degree days, base 40°F
4,657
Growing degree days, base 45°F
3,534
Growing degree days, base 50°F
2,568
Growing degree days, base 55°F
1,750
Growing degree days, base 60°F
1,079

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,19801
February1,03900
March907010
April555156
May27517227
June66102487
July8217674
August16167617
September12749374
October4474104
November714017
December1,02902

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 10 km from Weston. 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 USC00195175 (Natick). Public domain.