Tillamook County climate

Tillamook County Frost Dates and Growing Season

NOAA 1991-2020 normals for Tillamook 6SE, 3 km from Tillamook County, elevation 140 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tillamook 6SE. 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 5 and the first fall freeze around November 4, a growing season of about 219 days.

Median at 36°F
last May 7, first October 12
Median at 32°F
last April 5, first November 4
Median at 28°F
last February 19, first December 4

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 20May 16May 11May 7May 4Apr 30Apr 26Apr 18
32°FMay 4Apr 27Apr 19Apr 11Apr 5Mar 31Mar 25Mar 15Mar 1
28°FMar 26Mar 11Mar 3Feb 26Feb 19Feb 13Jan 31Jan 9Dec 17
24°FFeb 21Feb 11Feb 1Jan 18Jan 4Dec 28Dec 15Dec 7Nov 28
20°FFeb 15Feb 8Feb 1Jan 15Dec 31Dec 24Dec 19Dec 13Dec 9
16°F–––––––––

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 23Sep 30Oct 3Oct 6Oct 12Oct 16Oct 21Oct 27Nov 3
32°FOct 13Oct 21Oct 26Oct 31Nov 4Nov 10Nov 18Nov 26Dec 7
28°FNov 1Nov 12Nov 22Nov 29Dec 4Dec 12Dec 22Jan 5Feb 10
24°FNov 14Nov 30Dec 5Dec 10Dec 19Dec 27Jan 7Jan 29Feb 10
20°FDec 8Dec 12Dec 18Dec 22Dec 29Jan 9Feb 1Feb 6Feb 15
16°F–––––––––

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°F189178170164157152147140130
32°F264248237228219212203193180
28°F350331316306297286275262245
24°F365365365365365355340328311
20°F365365365365365365365365356
16°F365365365365365365365365365

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
94% of years
24°F or colder
50% of years
20°F or colder
14% of years
16°F or colder
1% 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
5,354
Cooling degree days, base 65°F
11
Growing degree days, base 40°F
3,891
Growing degree days, base 45°F
2,371
Growing degree days, base 50°F
1,227
Growing degree days, base 55°F
478
Growing degree days, base 60°F
99

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January67007
February589010
March608015
April521125
May420178
June2781174
July1871279
August1693299
September2285228
October416188
November570019
December69905

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 3 km from Tillamook County. 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 USC00358498 (Tillamook 6SE). Public domain.