Washington climate

Washington Frost Dates and Growing Season

NOAA 1991-2020 normals for Parkersburg, 10.1 km from Washington, elevation 620 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Parkersburg. 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 30, a growing season of about 197 days.

Median at 36°F
last April 26, first October 19
Median at 32°F
last April 14, first October 30
Median at 28°F
last April 1, first November 9

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 13May 7May 3Apr 30Apr 26Apr 23Apr 19Apr 17Apr 12
32°FMay 2Apr 25Apr 20Apr 17Apr 14Apr 10Apr 7Apr 4Mar 31
28°FApr 16Apr 11Apr 6Apr 3Apr 1Mar 30Mar 26Mar 22Mar 16
24°FApr 4Mar 31Mar 27Mar 24Mar 21Mar 18Mar 13Mar 9Mar 1
20°FMar 26Mar 21Mar 17Mar 12Mar 9Mar 5Mar 1Feb 25Feb 16
16°FMar 18Mar 12Mar 7Mar 3Feb 28Feb 24Feb 18Feb 11Feb 3

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 7Oct 12Oct 14Oct 17Oct 19Oct 22Oct 24Oct 27Oct 31
32°FOct 16Oct 21Oct 24Oct 27Oct 30Nov 1Nov 3Nov 7Nov 12
28°FOct 25Oct 31Nov 2Nov 6Nov 9Nov 12Nov 15Nov 19Nov 27
24°FNov 2Nov 8Nov 13Nov 16Nov 21Nov 26Dec 1Dec 4Dec 9
20°FNov 14Nov 22Nov 28Dec 1Dec 5Dec 9Dec 15Dec 22Dec 28
16°FNov 30Dec 6Dec 12Dec 18Dec 23Dec 27Jan 1Jan 6Jan 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°F192186182177174170165160152
32°F218211206202197193188182174
28°F243235230226221217213209202
24°F272263257250246241235229221
20°F300291284277272267260255245
16°F323314306302297291285278269

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
4,815
Cooling degree days, base 65°F
1,179
Growing degree days, base 40°F
6,299
Growing degree days, base 45°F
4,986
Growing degree days, base 50°F
3,824
Growing degree days, base 55°F
2,803
Growing degree days, base 60°F
1,921

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,01709
February839012
March679253
April32917201
May11990439
June14235672
July0349814
August1311775
September48151554
October29522227
November596157
December877012

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 10.1 km from Washington. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00013867 (Parkersburg). Public domain.