Clatskanie climate

Clatskanie Frost Dates and Growing Season

NOAA 1991-2020 normals for Clatskanie, 0.8 km from Clatskanie, elevation 22 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Clatskanie. 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 24 and the first fall freeze around October 24, a growing season of about 184 days.

Median at 36°F
last May 11, first October 7
Median at 32°F
last April 24, first October 24
Median at 28°F
last March 25, 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 30May 24May 19May 15May 11May 7May 4Apr 30Apr 24
32°FMay 9May 4May 1Apr 28Apr 24Apr 19Apr 14Apr 8Mar 31
28°FApr 20Apr 9Apr 4Mar 30Mar 25Mar 18Mar 12Mar 4Feb 25
24°FMar 18Mar 8Feb 28Feb 25Feb 20Feb 15Feb 6Jan 23Jan 3
20°FFeb 26Feb 19Feb 13Feb 2Jan 22Jan 8Jan 1Dec 19Dec 6
16°FFeb 18Feb 9Jan 26Jan 10Jan 1Dec 24Dec 14Dec 7Nov 29

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 24Sep 29Oct 2Oct 4Oct 7Oct 10Oct 14Oct 19Oct 27
32°FOct 5Oct 9Oct 15Oct 20Oct 24Oct 27Nov 1Nov 6Nov 12
28°FOct 20Oct 26Oct 30Nov 5Nov 9Nov 14Nov 20Nov 26Dec 4
24°FNov 3Nov 11Nov 19Nov 24Nov 30Dec 5Dec 13Dec 23Jan 5
20°FNov 18Nov 29Dec 5Dec 11Dec 19Dec 29Jan 5Jan 21Feb 12
16°FNov 24Dec 3Dec 8Dec 15Dec 25Jan 1Jan 8Jan 26Feb 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°F172165160154150145140133124
32°F210201195189184179173167159
28°F269255246239232224218211201
24°F335318307299290281272262249
20°F365365357346334327317306296
16°F365365365365365365362344330

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
98% of years
20°F or colder
77% of years
16°F or colder
33% 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
5,268
Cooling degree days, base 65°F
105
Growing degree days, base 40°F
4,190
Growing degree days, base 45°F
2,800
Growing degree days, base 50°F
1,724
Growing degree days, base 55°F
924
Growing degree days, base 60°F
384

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January78101
February65702
March623013
April494045
May3323157
June20111260
July8739417
August7241434
September16812295
October423088
November633011
December79801

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 0.8 km from Clatskanie. 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 USC00351643 (Clatskanie). Public domain.