Akutan climate

Akutan Frost Dates and Growing Season

NOAA 1991-2020 normals for Dutch Harbor, 56.8 km from Akutan, elevation 10 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dutch Harbor. 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 May 6 and the first fall freeze around October 18, a growing season of about 164 days.

Median at 36°F
last May 26, first October 1
Median at 32°F
last May 6, first October 18
Median at 28°F
last April 19, first November 4

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 11Jun 4Jun 1May 29May 26May 23May 19May 15May 10
32°FMay 22May 16May 12May 9May 6May 4May 1Apr 28Apr 23
28°FMay 5May 1Apr 26Apr 23Apr 19Apr 15Apr 12Apr 9Apr 3
24°FApr 17Apr 11Apr 7Apr 3Mar 31Mar 28Mar 22Mar 13Mar 1
20°FApr 3Mar 30Mar 24Mar 17Mar 8Mar 1Feb 20Feb 9Jan 26
16°FMar 29Mar 18Mar 7Feb 28Feb 19Feb 9Feb 1Jan 24Jan 1

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 4Sep 14Sep 20Sep 26Oct 1Oct 4Oct 8Oct 13Oct 19
32°FSep 20Oct 2Oct 8Oct 14Oct 18Oct 23Oct 27Nov 1Nov 5
28°FOct 10Oct 19Oct 26Nov 1Nov 4Nov 8Nov 13Nov 19Dec 1
24°FOct 23Nov 1Nov 6Nov 13Nov 22Dec 2Dec 11Dec 24Jan 4
20°FNov 1Nov 10Nov 22Dec 12Dec 28Jan 5Jan 14Jan 25Feb 12
16°FNov 10Nov 30Jan 2Jan 12Jan 21Jan 29Feb 5Feb 18Mar 7

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°F15114213713212612011410591
32°F188181174169164159153146133
28°F230219210203198192186177167
24°F283269257249240230222212200
20°F333316303290282274266251229
16°F365365360337327315303287273

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
73% 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
8,526
Cooling degree days, base 65°F
1
Growing degree days, base 40°F
1,571
Growing degree days, base 45°F
754
Growing degree days, base 50°F
250
Growing degree days, base 55°F
51
Growing degree days, base 60°F
7

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January99200
February86800
March95900
April83600
May71200
June530010
July403077
August3511121
September468039
October67402
November80300
December93200

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 56.8 km from Akutan. 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 USC00502587 (Dutch Harbor). Public domain.