Kettle Falls climate

Kettle Falls Frost Dates and Growing Season

NOAA 1991-2020 normals for Colville, 10.1 km from Kettle Falls, elevation 1554 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Colville. 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 2 and the first fall freeze around October 2, a growing season of about 153 days.

Median at 36°F
last May 17, first September 22
Median at 32°F
last May 2, first October 2
Median at 28°F
last April 15, first October 14

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 24May 20May 17May 14May 12May 7May 3
32°FMay 17May 12May 8May 5May 2Apr 30Apr 27Apr 24Apr 19
28°FMay 2Apr 27Apr 23Apr 19Apr 15Apr 10Apr 5Mar 31Mar 25
24°FApr 14Apr 4Mar 31Mar 27Mar 22Mar 17Mar 13Mar 9Mar 4
20°FMar 29Mar 19Mar 13Mar 9Mar 6Mar 3Feb 28Feb 24Feb 17
16°FMar 16Mar 8Mar 3Mar 1Feb 26Feb 22Feb 17Feb 10Jan 30

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 6Sep 12Sep 16Sep 19Sep 22Sep 25Sep 27Oct 1Oct 4
32°FSep 19Sep 25Sep 28Oct 1Oct 2Oct 5Oct 7Oct 12Oct 17
28°FOct 1Oct 4Oct 7Oct 11Oct 14Oct 18Oct 21Oct 26Nov 2
24°FOct 6Oct 14Oct 20Oct 24Oct 28Nov 1Nov 5Nov 10Nov 18
20°FOct 20Oct 27Nov 1Nov 6Nov 11Nov 16Nov 21Nov 27Dec 3
16°FOct 30Nov 9Nov 15Nov 21Nov 25Nov 29Dec 3Dec 10Dec 20

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°F148141136131127122117112104
32°F175166161157153149145140132
28°F210201194188183178173168159
24°F245235229223217211205198187
20°F279267259253247241235227217
16°F308297287279273265258249239

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
100% of years
16°F or colder
100% 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
6,307
Cooling degree days, base 65°F
458
Growing degree days, base 40°F
4,419
Growing degree days, base 45°F
3,300
Growing degree days, base 50°F
2,357
Growing degree days, base 55°F
1,568
Growing degree days, base 60°F
924

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12400
February89900
March73904
April483058
May24313249
June9750404
July20191635
August21168612
September15535335
October541059
November86401
December1,12100

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 10.1 km from Kettle Falls. 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 USC00451630 (Colville). Public domain.