Metlakatla climate

Metlakatla Frost Dates and Growing Season

NOAA 1991-2020 normals for Annette Island AP, 10 km from Metlakatla, elevation 109 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Annette Island 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 4 and the first fall freeze around October 31, a growing season of about 208 days.

Median at 36°F
last April 27, first October 16
Median at 32°F
last April 4, first October 31
Median at 28°F
last March 16, 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 10May 6May 2Apr 30Apr 27Apr 23Apr 20Apr 16Apr 10
32°FApr 22Apr 17Apr 12Apr 8Apr 4Apr 1Mar 30Mar 26Mar 20
28°FMar 31Mar 28Mar 23Mar 20Mar 16Mar 13Mar 8Mar 4Feb 26
24°FMar 18Mar 12Mar 8Mar 4Feb 28Feb 23Feb 15Feb 4Jan 20
20°FMar 6Feb 28Feb 21Feb 12Feb 2Jan 27Jan 17Jan 7Dec 25
16°FFeb 28Feb 16Feb 2Jan 27Jan 19Jan 11Jan 4Dec 30Dec 12

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 2Oct 5Oct 10Oct 13Oct 16Oct 19Oct 22Oct 26Oct 30
32°FOct 15Oct 21Oct 25Oct 28Oct 31Nov 4Nov 7Nov 13Nov 20
28°FOct 30Nov 5Nov 9Nov 14Nov 18Nov 22Nov 27Dec 1Dec 9
24°FNov 12Nov 19Nov 25Nov 29Dec 2Dec 9Dec 15Dec 25Jan 4
20°FNov 23Nov 30Dec 5Dec 11Dec 18Dec 26Jan 1Jan 12Jan 27
16°FNov 29Dec 7Dec 15Dec 26Jan 1Jan 6Jan 16Jan 25Feb 11

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°F193185179175171167163158152
32°F232223218212208203199192185
28°F277266258252246240235228218
24°F325311300293286275268260250
20°F361349338328317307300289272
16°F365365365359349340333317304

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
99% of years
20°F or colder
91% of years
16°F or colder
63% 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
6,325
Cooling degree days, base 65°F
28
Growing degree days, base 40°F
3,260
Growing degree days, base 45°F
2,016
Growing degree days, base 50°F
1,101
Growing degree days, base 55°F
459
Growing degree days, base 60°F
126

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January84601
February74601
March77301
April590013
May413190
June2635193
July17511301
August16411312
September2970158
October529029
November70103
December82801

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 km from Metlakatla. 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 USW00025308 (Annette Island AP). Public domain.