Jaffrey climate

Jaffrey Frost Dates and Growing Season

NOAA 1991-2020 normals for Jaffrey Silver Rch Airpark, 1.6 km from Jaffrey, elevation 1030 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jaffrey Silver Rch Airpark. 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 6, a growing season of about 154 days.

Median at 36°F
last May 17, first September 28
Median at 32°F
last May 5, first October 6
Median at 28°F
last April 21, first October 19

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 26May 23May 20May 17May 13May 10May 7May 3
32°FMay 19May 14May 10May 7May 5May 2Apr 30Apr 27Apr 22
28°FMay 6May 2Apr 28Apr 24Apr 21Apr 19Apr 16Apr 13Apr 7
24°FApr 20Apr 16Apr 13Apr 10Apr 8Apr 5Apr 3Apr 1Mar 29
20°FApr 10Apr 6Apr 4Apr 2Apr 1Mar 30Mar 27Mar 22Mar 16
16°FApr 3Mar 31Mar 28Mar 25Mar 22Mar 19Mar 16Mar 13Mar 9

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 15Sep 19Sep 22Sep 25Sep 28Sep 30Oct 2Oct 5Oct 9
32°FSep 25Sep 30Oct 1Oct 4Oct 6Oct 9Oct 12Oct 17Oct 22
28°FOct 3Oct 8Oct 12Oct 16Oct 19Oct 23Oct 27Nov 1Nov 5
24°FOct 15Oct 21Oct 26Oct 31Nov 2Nov 5Nov 8Nov 12Nov 17
20°FOct 28Nov 3Nov 7Nov 11Nov 14Nov 18Nov 21Nov 26Dec 1
16°FNov 11Nov 17Nov 21Nov 24Nov 27Nov 30Dec 2Dec 7Dec 13

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°F149144140136132129125120114
32°F175168162158154150146142135
28°F202194188183179174170165158
24°F226220215211207202197192183
20°F250242237232228224219214207
16°F271264258253249245241235227

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
7,048
Cooling degree days, base 65°F
519
Growing degree days, base 40°F
4,429
Growing degree days, base 45°F
3,384
Growing degree days, base 50°F
2,471
Growing degree days, base 55°F
1,690
Growing degree days, base 60°F
1,034

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,32300
February1,13800
March1,01808
April607146
May27317232
June6393482
July8204662
August19149595
September15654353
October501284
November810010
December1,13301

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 1.6 km from Jaffrey. 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 USC00274304 (Jaffrey Silver Rch Airpark). Public domain.