Faneuil climate

Faneuil Frost Dates and Growing Season

NOAA 1991-2020 normals for Jamaica Plain, 6.7 km from Faneuil, elevation 95 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jamaica Plain. 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 23, a growing season of about 185 days.

Median at 36°F
last May 2, first October 10
Median at 32°F
last April 19, first October 23
Median at 28°F
last April 5, first November 3

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 7May 4May 2Apr 30Apr 27Apr 24Apr 20
32°FMay 3Apr 28Apr 24Apr 21Apr 19Apr 16Apr 13Apr 10Apr 6
28°FApr 21Apr 16Apr 12Apr 9Apr 5Apr 3Apr 1Mar 30Mar 25
24°FApr 7Apr 3Apr 1Mar 31Mar 28Mar 24Mar 21Mar 17Mar 12
20°FMar 31Mar 27Mar 23Mar 20Mar 17Mar 14Mar 12Mar 8Mar 4
16°FMar 22Mar 18Mar 14Mar 12Mar 9Mar 6Mar 3Feb 28Feb 21

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 30Oct 3Oct 5Oct 8Oct 10Oct 12Oct 16Oct 20Oct 25
32°FOct 8Oct 12Oct 16Oct 20Oct 23Oct 25Oct 28Nov 1Nov 5
28°FOct 19Oct 26Oct 29Nov 1Nov 3Nov 6Nov 9Nov 13Nov 19
24°FNov 1Nov 5Nov 9Nov 12Nov 15Nov 19Nov 23Nov 28Dec 3
20°FNov 14Nov 20Nov 24Nov 28Dec 1Dec 3Dec 6Dec 10Dec 16
16°FNov 28Dec 2Dec 5Dec 8Dec 12Dec 15Dec 20Dec 23Dec 29

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°F181174169165161157155150144
32°F204198193189185182178172165
28°F230222217214210206202198191
24°F257248242238233229224219213
20°F281272267262257252247242235
16°F300292287282278274269263255

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
5,811
Cooling degree days, base 65°F
827
Growing degree days, base 40°F
5,269
Growing degree days, base 45°F
4,080
Growing degree days, base 50°F
3,047
Growing degree days, base 55°F
2,161
Growing degree days, base 60°F
1,421

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,14101
February97201
March853013
April501580
May22533285
June46146551
July4294755
August6248707
September8793457
October3698157
November648036
December95905

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 6.7 km from Faneuil. 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 USC00193890 (Jamaica Plain). Public domain.