Harrisville climate

Harrisville Frost Dates and Growing Season

NOAA 1991-2020 normals for Harrisville 2NNE, 3.1 km from Harrisville, elevation 585 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Harrisville 2NNE. 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 8 and the first fall freeze around October 16, a growing season of about 160 days.

Median at 36°F
last May 21, first October 4
Median at 32°F
last May 8, first October 16
Median at 28°F
last April 27, first October 29

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 4May 31May 28May 25May 21May 18May 15May 10May 6
32°FMay 24May 19May 15May 11May 8May 5May 2Apr 30Apr 26
28°FMay 12May 6May 3Apr 30Apr 27Apr 24Apr 21Apr 18Apr 13
24°FApr 29Apr 23Apr 20Apr 17Apr 14Apr 11Apr 8Apr 5Apr 2
20°FApr 17Apr 12Apr 8Apr 6Apr 4Apr 2Mar 31Mar 26Mar 21
16°FApr 8Apr 4Apr 1Mar 31Mar 26Mar 23Mar 20Mar 16Mar 13

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 23Sep 27Sep 30Oct 1Oct 4Oct 7Oct 10Oct 13Oct 17
32°FOct 2Oct 7Oct 10Oct 13Oct 16Oct 19Oct 21Oct 26Oct 30
28°FOct 15Oct 20Oct 24Oct 27Oct 29Nov 1Nov 3Nov 6Nov 12
24°FOct 29Nov 1Nov 4Nov 7Nov 11Nov 14Nov 16Nov 20Nov 25
20°FNov 6Nov 11Nov 15Nov 18Nov 21Nov 25Nov 28Dec 1Dec 7
16°FNov 14Nov 20Nov 25Nov 28Dec 1Dec 2Dec 6Dec 11Dec 19

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°F155148143139135131127122116
32°F178172168164160156151146140
28°F204197192187183180175171163
24°F228222217212209205201197191
20°F253245240235231227223218212
16°F271264258254250245241235229

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
8,233
Cooling degree days, base 65°F
192
Growing degree days, base 40°F
3,392
Growing degree days, base 45°F
2,470
Growing degree days, base 50°F
1,682
Growing degree days, base 55°F
1,029
Growing degree days, base 60°F
522

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,40300
February1,24700
March1,13801
April803010
May486385
June18725293
July5876484
August5170484
September21117268
October565156
November88103
December1,20400

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 3.1 km from Harrisville. 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 USC00203628 (Harrisville 2NNE). Public domain.