Northampton climate

Northampton Frost Dates and Growing Season

NOAA 1991-2020 normals for Amherst, 10.9 km from Northampton, elevation 145 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Amherst. 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 May 5 and the first fall freeze around October 8, a growing season of about 156 days.

Median at 36°F
last May 17, first September 30
Median at 32°F
last May 5, first October 8
Median at 28°F
last April 23, first October 21

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 30May 25May 22May 19May 17May 14May 10May 7May 3
32°FMay 19May 15May 11May 7May 5May 2Apr 30Apr 26Apr 23
28°FMay 7May 2Apr 30Apr 26Apr 23Apr 20Apr 18Apr 13Apr 9
24°FApr 23Apr 18Apr 14Apr 11Apr 7Apr 5Apr 3Apr 1Mar 28
20°FApr 8Apr 4Apr 2Mar 31Mar 29Mar 26Mar 22Mar 17Mar 12
16°FMar 31Mar 29Mar 25Mar 21Mar 18Mar 15Mar 11Mar 8Mar 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 17Sep 22Sep 26Sep 28Sep 30Oct 2Oct 4Oct 6Oct 11
32°FSep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 14Oct 18Oct 23
28°FOct 6Oct 10Oct 14Oct 18Oct 21Oct 24Oct 28Oct 31Nov 4
24°FOct 17Oct 22Oct 26Oct 30Nov 1Nov 3Nov 6Nov 10Nov 15
20°FOct 28Nov 1Nov 5Nov 8Nov 12Nov 15Nov 18Nov 24Nov 29
16°FNov 12Nov 16Nov 20Nov 23Nov 26Nov 30Dec 2Dec 6Dec 14

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°F151146142138134130127122116
32°F175168163159156152148143137
28°F199193187183179175171166159
24°F226218213209205201196190182
20°F251243238234229224221215208
16°F275267261256252247243238230

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
6,664
Cooling degree days, base 65°F
580
Growing degree days, base 40°F
4,630
Growing degree days, base 45°F
3,545
Growing degree days, base 50°F
2,598
Growing degree days, base 55°F
1,783
Growing degree days, base 60°F
1,109

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27401
February1,08801
March94106
April564359
May25925250
June61106496
July8214671
August18170617
September13858375
October4614107
November768016
December1,08501

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 10.9 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 USC00190120 (Amherst). Public domain.