Fairchild Air Force Base climate

Fairchild Air Force Base Frost Dates and Growing Season

NOAA 1991-2020 normals for Spokane WFO, 7.1 km from Fairchild Air Force Base, elevation 2392 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Spokane WFO. 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 10 and the first fall freeze around September 26, a growing season of about 137 days.

Median at 36°F
last May 31, first September 12
Median at 32°F
last May 10, first September 26
Median at 28°F
last April 25, first October 7

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 24Jun 15Jun 8Jun 3May 31May 27May 22May 18May 12
32°FMay 30May 22May 17May 13May 10May 7May 3Apr 30Apr 25
28°FMay 11May 5May 2Apr 29Apr 25Apr 22Apr 18Apr 13Apr 4
24°FApr 25Apr 17Apr 11Apr 4Mar 31Mar 28Mar 22Mar 16Mar 9
20°FApr 1Mar 24Mar 17Mar 13Mar 9Mar 6Mar 2Feb 27Feb 20
16°FMar 13Mar 8Mar 4Mar 1Feb 27Feb 23Feb 19Feb 13Feb 4

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°FAug 29Sep 3Sep 6Sep 9Sep 12Sep 15Sep 19Sep 22Sep 27
32°FSep 11Sep 16Sep 19Sep 23Sep 26Sep 29Oct 1Oct 4Oct 8
28°FSep 25Sep 30Oct 2Oct 4Oct 7Oct 10Oct 13Oct 17Oct 23
24°FOct 4Oct 9Oct 13Oct 17Oct 20Oct 23Oct 28Nov 1Nov 7
20°FOct 15Oct 21Oct 25Oct 29Nov 2Nov 7Nov 12Nov 19Nov 26
16°FOct 24Oct 31Nov 5Nov 11Nov 16Nov 21Nov 26Dec 1Dec 10

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°F12711911310710398938676
32°F158152147142137133127121113
28°F193183176171166160156150142
24°F235224217210205199192184173
20°F269258251244238232227219208
16°F298287278271265259252245234

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
7,066
Cooling degree days, base 65°F
289
Growing degree days, base 40°F
3,718
Growing degree days, base 45°F
2,690
Growing degree days, base 50°F
1,843
Growing degree days, base 55°F
1,158
Growing degree days, base 60°F
638

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,14700
February94500
March81702
April588028
May3575153
June19123285
July46126545
August47114532
September22721260
October612038
November91801
December1,17200

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 7.1 km from Fairchild Air Force Base. 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 USC00457941 (Spokane WFO). Public domain.