Northampton climate

Northampton Frost Dates and Growing Season

NOAA 1991-2020 normals for Allentown Intl AP, 5.6 km from Northampton, elevation 390 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Allentown Intl 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 20 and the first fall freeze around October 24, a growing season of about 184 days.

Median at 36°F
last May 2, first October 12
Median at 32°F
last April 20, first October 24
Median at 28°F
last April 5, first November 4

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 18May 12May 9May 5May 2Apr 30Apr 26Apr 22Apr 19
32°FMay 6Apr 30Apr 26Apr 23Apr 20Apr 17Apr 14Apr 11Apr 6
28°FApr 18Apr 13Apr 10Apr 7Apr 5Apr 2Mar 31Mar 29Mar 23
24°FApr 6Apr 2Mar 31Mar 29Mar 26Mar 22Mar 19Mar 15Mar 10
20°FMar 30Mar 25Mar 20Mar 17Mar 14Mar 11Mar 7Mar 3Feb 26
16°FMar 20Mar 15Mar 11Mar 7Mar 4Mar 1Feb 27Feb 21Feb 14

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 29Oct 2Oct 5Oct 9Oct 12Oct 15Oct 18Oct 22Oct 28
32°FOct 8Oct 13Oct 17Oct 21Oct 24Oct 27Oct 31Nov 2Nov 6
28°FOct 19Oct 26Oct 30Nov 1Nov 4Nov 6Nov 9Nov 13Nov 18
24°FNov 1Nov 6Nov 9Nov 12Nov 16Nov 19Nov 23Nov 28Dec 3
20°FNov 11Nov 16Nov 21Nov 24Nov 29Dec 1Dec 5Dec 9Dec 17
16°FNov 24Dec 1Dec 4Dec 8Dec 12Dec 18Dec 22Dec 28Jan 4

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°F182174169165161157153148142
32°F204198193189184180176170163
28°F229223219215211207202197190
24°F256249244239234230225221214
20°F283275269264259255249244236
16°F309300294289284279274268260

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
5,293
Cooling degree days, base 65°F
981
Growing degree days, base 40°F
5,749
Growing degree days, base 45°F
4,504
Growing degree days, base 50°F
3,405
Growing degree days, base 55°F
2,455
Growing degree days, base 60°F
1,646

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,08202
February91303
March755025
April4038131
May15160377
June19196627
July1328792
August3268730
September69108490
October33413186
November632038
December93206

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 5.6 km from Northampton. 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 USW00014737 (Allentown Intl AP). Public domain.