Wilmot climate

Wilmot Frost Dates and Growing Season

NOAA 1991-2020 normals for Portland, 22.5 km from Wilmot, elevation 128 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Portland. 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 March 14 and the first fall freeze around November 10, a growing season of about 241 days.

Median at 36°F
last March 28, first November 1
Median at 32°F
last March 14, first November 10
Median at 28°F
last March 2, first November 25

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°FApr 14Apr 7Apr 4Mar 31Mar 28Mar 25Mar 20Mar 14Mar 7
32°FApr 1Mar 27Mar 23Mar 18Mar 14Mar 11Mar 6Mar 1Feb 25
28°FMar 22Mar 15Mar 10Mar 6Mar 2Feb 28Feb 23Feb 18Feb 9
24°FMar 11Mar 5Feb 28Feb 23Feb 17Feb 11Feb 4Jan 30Jan 20
20°FMar 3Feb 21Feb 12Feb 5Jan 31Jan 27Jan 20Jan 11Dec 30
16°FFeb 20Feb 8Feb 1Jan 28Jan 22Jan 16Jan 9Jan 1Dec 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°FOct 20Oct 24Oct 28Oct 30Nov 1Nov 4Nov 6Nov 11Nov 18
32°FOct 28Nov 1Nov 4Nov 7Nov 10Nov 14Nov 19Nov 24Dec 1
28°FNov 4Nov 9Nov 15Nov 20Nov 25Nov 29Dec 1Dec 6Dec 16
24°FNov 15Nov 24Nov 29Dec 3Dec 8Dec 13Dec 21Jan 1Jan 9
20°FDec 1Dec 7Dec 13Dec 22Dec 29Jan 3Jan 9Jan 16Feb 1
16°FDec 11Dec 20Dec 29Jan 2Jan 7Jan 12Jan 17Jan 27Feb 6

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°F242234228222218213209204195
32°F266257251245241235230224217
28°F294284276270264258253247236
24°F330318309302294288279271260
20°F365355344335328320311304291
16°F365365365365361351343333320

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
99% of years
20°F or colder
86% of years
16°F or colder
53% 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
2,818
Cooling degree days, base 65°F
2,155
Growing degree days, base 40°F
8,667
Growing degree days, base 45°F
7,070
Growing degree days, base 50°F
5,610
Growing degree days, base 55°F
4,302
Growing degree days, base 60°F
3,150

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January692141
February525265
March34415199
April12366399
May18226673
June0416865
July0507972
August0496961
September6321765
October11194454
November37111161
December628256

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 22.5 km from Wilmot. 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 USC00035866 (Portland). Public domain.