Nahant climate

Nahant Frost Dates and Growing Season

NOAA 1991-2020 normals for Marblehead, 9.3 km from Nahant, elevation 84 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Marblehead. 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 20, a growing season of about 176 days.

Median at 36°F
last May 9, first October 9
Median at 32°F
last April 25, first October 20
Median at 28°F
last April 11, 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 26May 20May 17May 13May 9May 6May 3May 1Apr 26
32°FMay 13May 5May 1Apr 29Apr 25Apr 23Apr 19Apr 17Apr 12
28°FApr 27Apr 21Apr 17Apr 14Apr 11Apr 9Apr 6Apr 4Apr 1
24°FApr 12Apr 7Apr 4Apr 2Mar 31Mar 29Mar 26Mar 22Mar 18
20°FApr 3Mar 31Mar 29Mar 25Mar 21Mar 19Mar 16Mar 13Mar 8
16°FMar 28Mar 22Mar 19Mar 16Mar 13Mar 11Mar 8Mar 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 28Oct 1Oct 4Oct 6Oct 9Oct 12Oct 15Oct 18Oct 23
32°FOct 5Oct 11Oct 14Oct 18Oct 20Oct 23Oct 25Oct 30Nov 3
28°FOct 17Oct 22Oct 26Oct 29Oct 31Nov 2Nov 5Nov 9Nov 15
24°FOct 28Nov 2Nov 5Nov 9Nov 12Nov 15Nov 17Nov 21Nov 28
20°FNov 6Nov 13Nov 17Nov 21Nov 24Nov 27Dec 1Dec 4Dec 10
16°FNov 20Nov 26Nov 30Dec 2Dec 4Dec 8Dec 12Dec 17Dec 23

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°F170164160155152148143138132
32°F195190185180176172168163157
28°F220214209205201198193188180
24°F245237232228224220215210204
20°F267261254249245241236230221
16°F289281275270266260256249241

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
6,377
Cooling degree days, base 65°F
479
Growing degree days, base 40°F
4,511
Growing degree days, base 45°F
3,385
Growing degree days, base 50°F
2,421
Growing degree days, base 55°F
1,615
Growing degree days, base 60°F
968

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,17801
February1,01500
March92105
April592243
May32013185
June9877430
July13184636
August17150598
September12150381
October4143119
November696020
December99402

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 9.3 km from Nahant. 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 USC00194502 (Marblehead). Public domain.