Andover climate

Andover Frost Dates and Growing Season

NOAA 1991-2020 normals for Salisbury, 11.5 km from Andover, elevation 550 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Salisbury. 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 14 and the first fall freeze around September 29, a growing season of about 138 days.

Median at 36°F
last May 27, first September 20
Median at 32°F
last May 14, first September 29
Median at 28°F
last April 30, first October 9

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°FJun 6Jun 3Jun 1May 29May 27May 24May 20May 17May 12
32°FMay 28May 23May 20May 17May 14May 10May 7May 4Apr 30
28°FMay 16May 10May 6May 3Apr 30Apr 28Apr 26Apr 23Apr 18
24°FApr 30Apr 25Apr 21Apr 19Apr 16Apr 13Apr 10Apr 7Apr 3
20°FApr 17Apr 11Apr 8Apr 6Apr 4Apr 2Mar 31Mar 27Mar 20
16°FApr 6Apr 2Mar 31Mar 29Mar 25Mar 21Mar 18Mar 14Mar 10

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 6Sep 11Sep 14Sep 17Sep 20Sep 23Sep 25Sep 30Oct 3
32°FSep 14Sep 21Sep 23Sep 27Sep 29Oct 1Oct 4Oct 7Oct 13
28°FSep 26Oct 1Oct 3Oct 6Oct 9Oct 13Oct 19Oct 25Nov 1
24°FOct 6Oct 12Oct 17Oct 22Oct 27Oct 31Nov 4Nov 8Nov 15
20°FOct 22Oct 30Nov 3Nov 8Nov 13Nov 16Nov 20Nov 25Nov 30
16°FNov 9Nov 16Nov 19Nov 24Nov 27Nov 30Dec 2Dec 6Dec 12

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°F13612812412011611310910598
32°F157150145142138134130125117
28°F186177171166162158153148141
24°F217209203197192188182175167
20°F243236231226222217212205196
16°F268260254250246241237232224

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
7,417
Cooling degree days, base 65°F
325
Growing degree days, base 40°F
3,891
Growing degree days, base 45°F
2,884
Growing degree days, base 50°F
2,024
Growing degree days, base 55°F
1,307
Growing degree days, base 60°F
729

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,32800
February1,13300
March1,01402
April664132
May35511168
June11758393
July27133570
August4696514
September21425276
October551158
November818011
December1,15000

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 11.5 km from Andover. 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 USC00277833 (Salisbury). Public domain.