Andover climate

Andover Frost Dates and Growing Season

NOAA 1991-2020 normals for Andover 2, 3.9 km from Andover, elevation 822 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Andover 2. 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 19 and the first fall freeze around September 25, a growing season of about 129 days.

Median at 36°F
last May 31, first September 15
Median at 32°F
last May 19, first September 25
Median at 28°F
last May 6, first October 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°FJun 12Jun 8Jun 5Jun 2May 31May 28May 25May 22May 18
32°FJun 1May 27May 24May 21May 19May 16May 13May 10May 5
28°FMay 19May 15May 12May 8May 6May 4May 1Apr 29Apr 26
24°FMay 5May 2Apr 30Apr 27Apr 25Apr 23Apr 21Apr 18Apr 13
20°FApr 24Apr 21Apr 18Apr 15Apr 13Apr 10Apr 8Apr 6Apr 3
16°FApr 15Apr 10Apr 8Apr 6Apr 4Apr 2Apr 1Mar 29Mar 24

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 3Sep 7Sep 10Sep 12Sep 15Sep 18Sep 21Sep 23Sep 26
32°FSep 13Sep 17Sep 20Sep 23Sep 25Sep 28Oct 1Oct 3Oct 7
28°FSep 24Sep 28Oct 1Oct 2Oct 4Oct 7Oct 10Oct 14Oct 19
24°FOct 2Oct 6Oct 10Oct 14Oct 17Oct 21Oct 25Oct 30Nov 3
20°FOct 16Oct 20Oct 25Oct 29Nov 1Nov 3Nov 6Nov 10Nov 15
16°FOct 30Nov 3Nov 6Nov 9Nov 12Nov 15Nov 18Nov 21Nov 27

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°F122117113109105102989386
32°F147141137133129125122117112
28°F167161157154150147144140133
24°F193186182177173169166162156
20°F217211206202199195191186180
16°F237231227223220216212208203

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
8,940
Cooling degree days, base 65°F
168
Growing degree days, base 40°F
3,289
Growing degree days, base 45°F
2,386
Growing degree days, base 50°F
1,613
Growing degree days, base 55°F
975
Growing degree days, base 60°F
479

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,58200
February1,38200
March1,22002
April79809
May4213117
June16830317
July5876483
August7644432
September27716219
October648031
November95903
December1,35200

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 3.9 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 USC00170217 (Andover 2). Public domain.