Nantucket climate

Nantucket Frost Dates and Growing Season

NOAA 1991-2020 normals for Nantucket Mem AP, 4.7 km from Nantucket, elevation 45 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Nantucket Mem AP. 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 13 and the first fall freeze around November 8, a growing season of about 208 days.

Median at 36°F
last April 28, first October 26
Median at 32°F
last April 13, first November 8
Median at 28°F
last March 31, first November 23

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 11May 6May 3Apr 30Apr 28Apr 25Apr 23Apr 20Apr 17
32°FApr 27Apr 22Apr 19Apr 16Apr 13Apr 11Apr 8Apr 5Apr 2
28°FApr 12Apr 7Apr 5Apr 3Mar 31Mar 30Mar 27Mar 22Mar 17
24°FApr 1Mar 28Mar 23Mar 20Mar 17Mar 14Mar 10Mar 6Mar 1
20°FMar 22Mar 16Mar 12Mar 9Mar 6Mar 3Feb 28Feb 24Feb 17
16°FMar 11Mar 6Mar 1Feb 27Feb 22Feb 17Feb 10Feb 4Jan 27

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 13Oct 18Oct 21Oct 24Oct 26Oct 29Nov 1Nov 5Nov 9
32°FOct 25Oct 31Nov 3Nov 5Nov 8Nov 12Nov 15Nov 18Nov 23
28°FNov 5Nov 11Nov 15Nov 20Nov 23Nov 25Nov 28Dec 1Dec 6
24°FNov 19Nov 25Nov 29Dec 1Dec 4Dec 7Dec 11Dec 16Dec 22
20°FDec 2Dec 6Dec 10Dec 15Dec 19Dec 22Dec 25Dec 30Jan 7
16°FDec 11Dec 18Dec 23Dec 29Jan 1Jan 5Jan 9Jan 15Jan 25

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°F198193187184180176172167160
32°F228222217212208205200196190
28°F256248243238235230226220214
24°F284277272266261256252247239
20°F309302296291286282276270262
16°F335327321314309305301295286

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
99% 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
5,536
Cooling degree days, base 65°F
343
Growing degree days, base 40°F
4,634
Growing degree days, base 45°F
3,385
Growing degree days, base 50°F
2,344
Growing degree days, base 55°F
1,493
Growing degree days, base 60°F
823

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January99000
February88100
March84201
April585016
May3461138
June10723366
July11135589
August11137591
September8344411
October3064186
November558039
December81707

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 4.7 km from Nantucket. 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 USW00014756 (Nantucket Mem AP). Public domain.