Willamina climate

Willamina Frost Dates and Growing Season

NOAA 1991-2020 normals for Laurel Mtn, 18.7 km from Willamina, elevation 3589 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Laurel Mtn. 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 20 and the first fall freeze around October 23, a growing season of about 157 days.

Median at 36°F
last June 10, first October 4
Median at 32°F
last May 20, first October 23
Median at 28°F
last April 27, first November 10

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 30Jun 23Jun 18Jun 14Jun 10Jun 7Jun 3May 31May 24
32°FJun 8Jun 2May 30May 26May 20May 15May 9May 3Apr 28
28°FMay 20May 10May 5Apr 30Apr 27Apr 24Apr 20Apr 13Mar 31
24°FApr 27Apr 18Apr 9Apr 2Mar 28Mar 21Mar 9Feb 25Feb 8
20°FMar 29Mar 14Mar 2Feb 24Feb 14Feb 3Jan 19Jan 5Dec 20
16°FFeb 24Feb 16Feb 7Jan 30Jan 12Jan 3Dec 28Dec 15Dec 6

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 9Sep 22Sep 28Oct 1Oct 4Oct 7Oct 11Oct 15Oct 21
32°FOct 5Oct 13Oct 16Oct 20Oct 23Oct 26Oct 30Nov 4Nov 9
28°FOct 23Oct 29Nov 2Nov 7Nov 10Nov 14Nov 18Nov 24Dec 1
24°FNov 1Nov 10Nov 16Nov 23Nov 28Dec 2Dec 7Dec 17Dec 31
20°FNov 11Nov 23Dec 1Dec 7Dec 17Dec 25Jan 1Jan 11Feb 6
16°FNov 24Dec 3Dec 9Dec 18Dec 27Jan 1Jan 8Jan 26Feb 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°F1411311261211151111049787
32°F185177170164157152146141131
28°F230218212205199193186180170
24°F301281269257248238229220206
20°F361340329318308299284272253
16°F365365365360346335327317306

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
91% of years
16°F or colder
61% 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
6,961
Cooling degree days, base 65°F
139
Growing degree days, base 40°F
3,065
Growing degree days, base 45°F
2,029
Growing degree days, base 50°F
1,262
Growing degree days, base 55°F
714
Growing degree days, base 60°F
351

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January85907
February79204
March85604
April744020
May547379
June39410130
July19344325
August15853362
September25927240
October521377
November741011
December89704

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 18.7 km from Willamina. 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 USC00354776 (Laurel Mtn). Public domain.