Tonasket climate

Tonasket Frost Dates and Growing Season

NOAA 1991-2020 normals for Tonasket 11NE, 16.7 km from Tonasket, elevation 3434 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tonasket 11NE. 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 6, a growing season of about 151 days.

Median at 36°F
last May 25, first September 25
Median at 32°F
last May 6, first October 6
Median at 28°F
last April 19, first October 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°FJun 15Jun 7Jun 3May 30May 25May 21May 17May 13May 9
32°FMay 25May 18May 13May 9May 6May 3Apr 30Apr 27Apr 23
28°FMay 5Apr 30Apr 26Apr 22Apr 19Apr 16Apr 12Apr 9Apr 4
24°FApr 14Apr 9Apr 5Apr 3Mar 31Mar 29Mar 25Mar 22Mar 15
20°FMar 30Mar 25Mar 20Mar 17Mar 14Mar 11Mar 8Mar 5Mar 1
16°FMar 17Mar 12Mar 8Mar 6Mar 4Mar 1Feb 27Feb 21Feb 16

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 12Sep 17Sep 20Sep 23Sep 25Sep 28Sep 30Oct 3Oct 6
32°FSep 24Sep 28Oct 1Oct 3Oct 6Oct 9Oct 12Oct 15Oct 18
28°FOct 4Oct 8Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Oct 31
24°FOct 14Oct 19Oct 22Oct 25Oct 28Oct 30Nov 2Nov 6Nov 11
20°FOct 23Oct 29Nov 1Nov 5Nov 8Nov 12Nov 15Nov 20Nov 24
16°FNov 1Nov 8Nov 12Nov 16Nov 21Nov 23Nov 26Nov 30Dec 6

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°F14213513012512011511110597
32°F170164159154151147142137128
28°F201196190185181176171166161
24°F232224218215210206201196189
20°F258251246241236232227222214
16°F284275268264259255251245237

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
8,323
Cooling degree days, base 65°F
170
Growing degree days, base 40°F
3,089
Growing degree days, base 45°F
2,196
Growing degree days, base 50°F
1,454
Growing degree days, base 55°F
867
Growing degree days, base 60°F
436

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,31600
February1,08900
March98000
April695010
May451093
June27215211
July8878456
August7665454
September28712204
October699026
November1,03800
December1,33300

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 16.7 km from Tonasket. 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 USC00458521 (Tonasket 11NE). Public domain.