Poolesville climate

Poolesville Frost Dates and Growing Season

NOAA 1991-2020 normals for Damascus 3 Ssw, 20.7 km from Poolesville, elevation 700 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Damascus 3 Ssw. 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 April 14 and the first fall freeze around October 29, a growing season of about 196 days.

Median at 36°F
last April 28, first October 17
Median at 32°F
last April 14, first October 29
Median at 28°F
last April 2, first November 8

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 15May 8May 4May 1Apr 28Apr 24Apr 22Apr 18Apr 14
32°FMay 2Apr 25Apr 20Apr 17Apr 14Apr 11Apr 7Apr 3Mar 31
28°FApr 16Apr 11Apr 7Apr 4Apr 2Mar 31Mar 28Mar 25Mar 18
24°FApr 5Apr 1Mar 29Mar 26Mar 23Mar 19Mar 16Mar 11Mar 5
20°FMar 27Mar 22Mar 19Mar 16Mar 12Mar 9Mar 5Feb 28Feb 23
16°FMar 20Mar 15Mar 10Mar 6Mar 3Feb 27Feb 22Feb 16Feb 6

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 5Oct 9Oct 12Oct 14Oct 17Oct 20Oct 24Oct 27Oct 31
32°FOct 13Oct 18Oct 23Oct 26Oct 29Nov 1Nov 3Nov 6Nov 12
28°FOct 26Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15Nov 19Nov 24
24°FNov 5Nov 9Nov 13Nov 16Nov 20Nov 25Nov 30Dec 4Dec 12
20°FNov 15Nov 22Nov 28Dec 2Dec 6Dec 10Dec 16Dec 22Dec 28
16°FDec 1Dec 7Dec 14Dec 20Dec 24Dec 28Jan 1Jan 7Jan 16

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°F192185181176171167163159152
32°F216210205201196192187181174
28°F242235228223220216212207201
24°F271263255249245241236230223
20°F298289284277272265260253244
16°F322313306301296291285278269

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
4,977
Cooling degree days, base 65°F
991
Growing degree days, base 40°F
5,958
Growing degree days, base 45°F
4,669
Growing degree days, base 50°F
3,528
Growing degree days, base 55°F
2,533
Growing degree days, base 60°F
1,686

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,02906
February85808
March703144
April36416169
May14067395
June19195625
July1315780
August3270732
September61111500
October31016207
November605148
December884013

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 20.7 km from Poolesville. 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 USC00182336 (Damascus 3 Ssw). Public domain.