Clackamas County climate

Clackamas County Frost Dates and Growing Season

NOAA 1991-2020 normals for Estacada 2 Se, 11.8 km from Clackamas County, elevation 514 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Estacada 2 Se. 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 March 27 and the first fall freeze around November 14, a growing season of about 230 days.

Median at 36°F
last April 25, first October 25
Median at 32°F
last March 27, first November 14
Median at 28°F
last February 22, first December 3

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 11May 5May 2Apr 29Apr 25Apr 21Apr 16Apr 11Apr 3
32°FApr 23Apr 14Apr 5Apr 1Mar 27Mar 23Mar 17Mar 11Mar 2
28°FMar 20Mar 9Mar 1Feb 26Feb 22Feb 17Feb 11Feb 2Jan 15
24°FFeb 22Feb 14Feb 7Jan 31Jan 21Jan 11Jan 2Dec 24Dec 12
20°FFeb 14Feb 1Jan 21Jan 11Jan 2Dec 25Dec 20Dec 13Dec 2
16°FJan 23Jan 10Jan 2Dec 31Dec 24Dec 21Dec 18Dec 13Dec 7

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°FOct 8Oct 15Oct 19Oct 22Oct 25Oct 28Nov 1Nov 6Nov 14
32°FOct 23Oct 30Nov 4Nov 9Nov 14Nov 18Nov 24Nov 29Dec 7
28°FNov 9Nov 16Nov 23Nov 28Dec 3Dec 7Dec 15Dec 23Jan 2
24°FNov 21Nov 30Dec 7Dec 12Dec 19Dec 26Jan 1Jan 10Feb 1
20°FNov 30Dec 5Dec 11Dec 18Dec 23Dec 30Jan 4Jan 18Feb 3
16°FDec 3Dec 10Dec 15Dec 19Dec 22Dec 30Jan 1Jan 5Jan 20

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°F213202196189185179173166158
32°F263253244237230224216209198
28°F326310301292286279271263249
24°F365365357348337331321311299
20°F365365365365365365355342331
16°F365365365365365365365365361

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
99% of years
24°F or colder
78% of years
20°F or colder
35% of years
16°F or colder
11% 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
4,362
Cooling degree days, base 65°F
356
Growing degree days, base 40°F
5,250
Growing degree days, base 45°F
3,715
Growing degree days, base 50°F
2,472
Growing degree days, base 55°F
1,528
Growing degree days, base 60°F
823

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January71005
February582011
March541036
April408391
May24915239
June12838360
July28120556
August23127569
September9450407
October3254165
November548029
December72705

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 11.8 km from Clackamas 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 USC00352693 (Estacada 2 Se). Public domain.