Ketchikan climate

Ketchikan Frost Dates and Growing Season

NOAA 1991-2020 normals for Beaver Falls, 3.5 km from Ketchikan, elevation 35 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Beaver Falls. 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 November 9, a growing season of about 218 days.

Median at 36°F
last April 27, first October 22
Median at 32°F
last April 4, first November 9
Median at 28°F
last March 13, first November 26

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 6May 2Apr 29Apr 27Apr 24Apr 19Apr 15Apr 8
32°FApr 25Apr 19Apr 13Apr 9Apr 4Mar 31Mar 28Mar 23Mar 15
28°FApr 5Mar 28Mar 22Mar 17Mar 13Mar 8Mar 3Feb 27Feb 15
24°FMar 17Mar 9Mar 3Feb 26Feb 20Feb 9Jan 29Jan 17Jan 6
20°FMar 11Mar 2Feb 21Feb 8Jan 29Jan 21Jan 10Jan 3Dec 17
16°FMar 5Feb 23Feb 7Jan 31Jan 22Jan 13Jan 4Dec 28Dec 9

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 5Oct 12Oct 16Oct 20Oct 22Oct 26Oct 29Nov 1Nov 8
32°FOct 19Oct 26Nov 1Nov 5Nov 9Nov 14Nov 19Nov 24Dec 2
28°FNov 4Nov 12Nov 17Nov 22Nov 26Nov 30Dec 5Dec 11Dec 22
24°FNov 13Nov 22Nov 30Dec 4Dec 9Dec 18Dec 26Jan 2Jan 16
20°FNov 26Dec 4Dec 11Dec 22Dec 29Jan 3Jan 11Jan 23Feb 8
16°FDec 1Dec 8Dec 20Jan 1Jan 6Jan 14Jan 24Feb 1Feb 25

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°F202194188183178174169164156
32°F248238230223218212206201191
28°F298284274266259252245239228
24°F342327317306298290280271256
20°F365364354343334324311299282
16°F365365365365364351341328305

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
80% of years
16°F or colder
48% 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
6,476
Cooling degree days, base 65°F
32
Growing degree days, base 40°F
3,207
Growing degree days, base 45°F
2,042
Growing degree days, base 50°F
1,165
Growing degree days, base 55°F
525
Growing degree days, base 60°F
155

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January90800
February77800
March78001
April594012
May3981106
June2488215
July16013318
August14911327
September2940162
October539025
November74300
December88500

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 3.5 km from Ketchikan. 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 USC00500657 (Beaver Falls). Public domain.