Corvallis climate

Corvallis Frost Dates and Growing Season

NOAA 1991-2020 normals for Western Ag Rsch Ctr, 2.7 km from Corvallis, elevation 3608 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Western Ag Rsch Ctr. 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 23 and the first fall freeze around September 21, a growing season of about 118 days.

Median at 36°F
last June 12, first September 8
Median at 32°F
last May 23, first September 21
Median at 28°F
last May 5, first October 2

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°FJul 1Jun 24Jun 20Jun 16Jun 12Jun 10Jun 5Jun 2May 27
32°FJun 10Jun 3May 31May 27May 23May 19May 16May 12May 8
28°FMay 19May 14May 11May 8May 5May 3Apr 30Apr 27Apr 22
24°FMay 8May 4Apr 30Apr 27Apr 23Apr 20Apr 15Apr 10Apr 3
20°FApr 24Apr 17Apr 12Apr 7Apr 3Mar 31Mar 26Mar 19Mar 10
16°FApr 5Mar 30Mar 24Mar 18Mar 13Mar 7Mar 4Feb 28Feb 22

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 24Aug 30Sep 1Sep 4Sep 8Sep 11Sep 14Sep 17Sep 22
32°FSep 5Sep 11Sep 15Sep 18Sep 21Sep 24Sep 27Oct 1Oct 4
28°FSep 16Sep 22Sep 26Sep 29Oct 2Oct 4Oct 7Oct 10Oct 16
24°FSep 28Oct 3Oct 7Oct 11Oct 14Oct 17Oct 20Oct 24Oct 29
20°FOct 7Oct 15Oct 20Oct 22Oct 27Oct 30Nov 1Nov 5Nov 11
16°FOct 20Oct 27Nov 1Nov 3Nov 6Nov 9Nov 13Nov 19Nov 25

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°F1059893888480746859
32°F14013312812311811310810294
28°F166160155151148144140134126
24°F196189183177173169163157150
20°F232222216210205199194187177
16°F265254248242236230224216205

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
7,256
Cooling degree days, base 65°F
252
Growing degree days, base 40°F
3,644
Growing degree days, base 45°F
2,625
Growing degree days, base 50°F
1,789
Growing degree days, base 55°F
1,111
Growing degree days, base 60°F
599

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,16600
February95501
March84203
April614027
May3783139
June18124297
July40127552
August5888497
September24710232
October625039
November94902
December1,20300

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 2.7 km from Corvallis. 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 USC00248783 (Western Ag Rsch Ctr). Public domain.