Spokane climate

Spokane Frost Dates and Growing Season

NOAA 1991-2020 normals for Spokane Intl AP, 8.6 km from Spokane, elevation 2353 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Spokane Intl 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 26 and the first fall freeze around October 12, a growing season of about 168 days.

Median at 36°F
last May 8, first October 1
Median at 32°F
last April 26, first October 12
Median at 28°F
last April 6, first October 23

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 26May 20May 15May 12May 8May 6May 3Apr 30Apr 26
32°FMay 10May 5May 2Apr 29Apr 26Apr 23Apr 20Apr 15Apr 9
28°FApr 28Apr 21Apr 15Apr 11Apr 6Apr 2Mar 29Mar 23Mar 15
24°FApr 4Mar 30Mar 25Mar 19Mar 13Mar 9Mar 6Mar 2Feb 26
20°FMar 17Mar 11Mar 7Mar 4Mar 1Feb 26Feb 21Feb 15Feb 6
16°FMar 8Mar 3Feb 28Feb 24Feb 19Feb 14Feb 6Jan 31Jan 15

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 17Sep 23Sep 27Sep 29Oct 1Oct 4Oct 7Oct 10Oct 14
32°FSep 29Oct 3Oct 6Oct 9Oct 12Oct 15Oct 18Oct 22Oct 28
28°FOct 7Oct 13Oct 16Oct 20Oct 23Oct 27Oct 30Nov 3Nov 10
24°FOct 16Oct 22Oct 26Oct 30Nov 3Nov 7Nov 11Nov 17Nov 25
20°FOct 26Nov 2Nov 7Nov 12Nov 18Nov 22Nov 27Dec 1Dec 9
16°FNov 5Nov 13Nov 21Nov 25Nov 30Dec 3Dec 9Dec 15Dec 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°F163157153149144140135130122
32°F192183177173168163159155147
28°F227218211205200194189182174
24°F260251244237231225219212203
20°F294281273266260254247241232
16°F322308299290283277270262252

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
6,463
Cooling degree days, base 65°F
515
Growing degree days, base 40°F
4,326
Growing degree days, base 45°F
3,227
Growing degree days, base 50°F
2,313
Growing degree days, base 55°F
1,560
Growing degree days, base 60°F
958

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,09700
February89900
March77404
April542043
May29415212
June13452369
July26212651
August28190628
September16245340
October532165
November86102
December1,11400

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 8.6 km from Spokane. 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 USW00024157 (Spokane Intl AP). Public domain.