Klawock climate

Klawock Frost Dates and Growing Season

NOAA 1991-2020 normals for Klawock AP, 3.4 km from Klawock, elevation 12 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Klawock AP. 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 29 and the first fall freeze around October 16, a growing season of about 169 days.

Median at 36°F
last May 19, first October 1
Median at 32°F
last April 29, first October 16
Median at 28°F
last April 9, first November 5

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

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 19Sep 22Sep 26Sep 29Oct 1Oct 4Oct 7Oct 11Oct 17
32°FOct 1Oct 6Oct 10Oct 13Oct 16Oct 20Oct 24Oct 29Nov 5
28°FOct 14Oct 22Oct 27Nov 1Nov 5Nov 9Nov 15Nov 22Nov 28
24°FNov 2Nov 10Nov 16Nov 22Nov 26Dec 1Dec 5Dec 13Dec 23
20°FNov 16Nov 25Dec 1Dec 8Dec 13Dec 21Dec 30Jan 10Jan 27
16°FNov 29Dec 6Dec 14Dec 24Jan 1Jan 8Jan 18Jan 29Feb 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°F156149144140136131127122116
32°F194184179175169165160154147
28°F239230222215209204198191181
24°F288276265259252246239232222
20°F342325314305297288279269255
16°F365365356345336327313304291

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
97% of years
16°F or colder
76% 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
7,216
Cooling degree days, base 65°F
6
Growing degree days, base 40°F
2,618
Growing degree days, base 45°F
1,528
Growing degree days, base 50°F
728
Growing degree days, base 55°F
218
Growing degree days, base 60°F
32

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January92100
February81600
March84201
April66205
May498040
June3481111
July2564213
August2351231
September3510112
October598013
November78301
December90701

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 3.4 km from Klawock. 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 USW00025367 (Klawock AP). Public domain.