Andover climate

Andover Frost Dates and Growing Season

NOAA 1991-2020 normals for Andover 1N, 2.3 km from Andover, elevation 899 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Andover 1N. 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 2, a growing season of about 148 days.

Median at 36°F
last May 16, first September 24
Median at 32°F
last May 5, first October 2
Median at 28°F
last April 25, first October 13

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 31May 27May 23May 20May 16May 13May 10May 7May 2
32°FMay 21May 16May 11May 8May 5May 2Apr 30Apr 27Apr 23
28°FMay 9May 5May 1Apr 28Apr 25Apr 22Apr 19Apr 16Apr 11
24°FApr 29Apr 24Apr 20Apr 17Apr 15Apr 12Apr 9Apr 6Apr 3
20°FApr 20Apr 15Apr 12Apr 9Apr 7Apr 5Apr 3Mar 31Mar 25
16°FApr 12Apr 7Apr 5Apr 3Apr 1Mar 29Mar 25Mar 21Mar 17

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 10Sep 15Sep 18Sep 21Sep 24Sep 27Sep 30Oct 2Oct 6
32°FSep 18Sep 23Sep 27Sep 30Oct 2Oct 5Oct 7Oct 12Oct 16
28°FSep 27Oct 3Oct 6Oct 10Oct 13Oct 16Oct 19Oct 22Oct 27
24°FOct 10Oct 15Oct 18Oct 22Oct 25Oct 27Oct 30Nov 2Nov 6
20°FOct 22Oct 26Oct 29Nov 1Nov 3Nov 5Nov 7Nov 11Nov 15
16°FOct 31Nov 2Nov 5Nov 7Nov 10Nov 12Nov 15Nov 19Nov 24

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°F149143138134129126122118109
32°F168161156152148144140135128
28°F189182177172168164160154148
24°F209203198194190186182176169
20°F227221216212208204200195189
16°F243236231226223219215210204

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
8,283
Cooling degree days, base 65°F
508
Growing degree days, base 40°F
4,272
Growing degree days, base 45°F
3,279
Growing degree days, base 50°F
2,396
Growing degree days, base 55°F
1,635
Growing degree days, base 60°F
998

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,63000
February1,33400
March1,095010
April637152
May28924232
June6397485
July13196647
August32138570
September19647317
October568578
November99506
December1,43200

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 2.3 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 USC00210190 (Andover 1N). Public domain.