Wrangell climate

Wrangell Frost Dates and Growing Season

NOAA 1991-2020 normals for Wrangell AP, 0.7 km from Wrangell, elevation 56 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wrangell 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 11 and the first fall freeze around November 1, a growing season of about 202 days.

Median at 36°F
last April 30, first October 16
Median at 32°F
last April 11, first November 1
Median at 28°F
last March 24, first November 18

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 14May 8May 5May 3Apr 30Apr 28Apr 24Apr 20Apr 16
32°FApr 29Apr 23Apr 19Apr 14Apr 11Apr 7Apr 4Mar 31Mar 26
28°FApr 9Apr 3Mar 31Mar 28Mar 24Mar 20Mar 15Mar 11Mar 4
24°FMar 25Mar 20Mar 14Mar 11Mar 6Mar 1Feb 24Feb 18Feb 5
20°FMar 14Mar 6Feb 28Feb 23Feb 17Feb 7Jan 28Jan 18Jan 5
16°FMar 8Feb 26Feb 17Feb 6Jan 27Jan 19Jan 13Jan 5Dec 20

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 30Oct 4Oct 8Oct 13Oct 16Oct 19Oct 22Oct 27Nov 1
32°FOct 13Oct 20Oct 25Oct 28Nov 1Nov 5Nov 9Nov 13Nov 19
28°FOct 31Nov 7Nov 11Nov 14Nov 18Nov 22Nov 25Nov 30Dec 7
24°FNov 13Nov 19Nov 24Nov 27Dec 1Dec 6Dec 11Dec 18Dec 28
20°FNov 24Nov 30Dec 5Dec 11Dec 18Dec 24Dec 30Jan 7Jan 18
16°FDec 1Dec 8Dec 15Dec 24Dec 30Jan 4Jan 11Jan 19Feb 1

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°F186179174171167163158153146
32°F225217211207202197192186179
28°F265257249244239233227221212
24°F306294285278270264258252245
20°F348333323313305296287279268
16°F365361352344335329317306289

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
81% 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
7,317
Cooling degree days, base 65°F
4
Growing degree days, base 40°F
2,670
Growing degree days, base 45°F
1,619
Growing degree days, base 50°F
821
Growing degree days, base 55°F
278
Growing degree days, base 60°F
49

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,00600
February86000
March85900
April64705
May440071
June2952161
July2191247
August2321234
September369094
October612010
November81500
December96400

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 0.7 km from Wrangell. 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 USC00509919 (Wrangell AP). Public domain.