Millwood climate

Millwood Frost Dates and Growing Season

NOAA 1991-2020 normals for Spokane Felts Fld, 2.9 km from Millwood, elevation 1953 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Spokane Felts Fld. 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 15, a growing season of about 170 days.

Median at 36°F
last May 9, first October 1
Median at 32°F
last April 26, first October 15
Median at 28°F
last April 4, first October 27

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 25May 18May 15May 12May 9May 7May 4May 1Apr 27
32°FMay 10May 5May 1Apr 29Apr 26Apr 24Apr 20Apr 17Apr 10
28°FApr 26Apr 19Apr 13Apr 8Apr 4Mar 31Mar 27Mar 22Mar 16
24°FMar 30Mar 25Mar 19Mar 15Mar 12Mar 8Mar 5Mar 2Feb 25
20°FMar 14Mar 8Mar 4Mar 1Feb 27Feb 23Feb 18Feb 12Feb 2
16°FMar 5Feb 28Feb 22Feb 18Feb 13Feb 7Feb 1Jan 22Jan 8

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 19Sep 24Sep 27Sep 29Oct 1Oct 3Oct 6Oct 10Oct 15
32°FSep 30Oct 4Oct 7Oct 11Oct 15Oct 17Oct 21Oct 25Oct 31
28°FOct 11Oct 17Oct 21Oct 24Oct 27Oct 30Nov 2Nov 7Nov 13
24°FOct 21Oct 29Nov 1Nov 4Nov 8Nov 11Nov 16Nov 21Nov 26
20°FNov 1Nov 7Nov 12Nov 18Nov 22Nov 26Dec 1Dec 6Dec 16
16°FNov 11Nov 18Nov 25Dec 1Dec 5Dec 10Dec 16Dec 23Jan 2

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°F162155151146143139135130124
32°F193184179174170165161156149
28°F231222217211205200196189179
24°F267258251246241236231224216
20°F302290282275269263257250242
16°F335324313304297290282274262

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
99% 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
6,019
Cooling degree days, base 65°F
507
Growing degree days, base 40°F
4,519
Growing degree days, base 45°F
3,363
Growing degree days, base 50°F
2,402
Growing degree days, base 55°F
1,610
Growing degree days, base 60°F
975

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,02900
February85100
March72905
April507049
May26514230
June11053394
July15218668
August18184631
September14638346
October492175
November81304
December1,04500

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 2.9 km from Millwood. 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 USW00094176 (Spokane Felts Fld). Public domain.