Benton County climate

Benton County Frost Dates and Growing Season

NOAA 1991-2020 normals for Corvallis Water Bureau, 2.9 km from Benton County, elevation 592 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Corvallis Water Bureau. 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 15 and the first fall freeze around October 8, a growing season of about 145 days.

Median at 36°F
last June 8, first September 19
Median at 32°F
last May 15, first October 8
Median at 28°F
last April 25, first October 28

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 26Jun 21Jun 17Jun 12Jun 8Jun 4May 31May 28May 21
32°FJun 2May 29May 23May 19May 15May 12May 7May 2Apr 28
28°FMay 10May 5May 1Apr 29Apr 25Apr 21Apr 17Apr 12Apr 2
24°FApr 20Apr 10Apr 3Mar 28Mar 22Mar 13Mar 5Feb 28Feb 19
20°FMar 4Feb 26Feb 19Feb 13Feb 3Jan 28Jan 14Jan 4Dec 18
16°FFeb 16Feb 1Jan 23Jan 11Jan 4Dec 31Dec 21Dec 11Nov 30

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 3Sep 6Sep 10Sep 15Sep 19Sep 23Sep 26Oct 1Oct 5
32°FSep 24Sep 29Oct 1Oct 5Oct 8Oct 12Oct 15Oct 19Oct 26
28°FOct 9Oct 17Oct 21Oct 25Oct 28Oct 30Nov 2Nov 7Nov 13
24°FOct 29Nov 2Nov 7Nov 11Nov 14Nov 18Nov 23Nov 28Dec 7
20°FNov 8Nov 15Nov 21Nov 27Dec 1Dec 8Dec 16Dec 25Jan 7
16°FNov 18Nov 27Dec 3Dec 11Dec 19Dec 26Jan 1Jan 8Jan 26

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°F12812011410810298928576
32°F172163157152145141135128119
28°F214203197191186181176170159
24°F280265254245237231223214203
20°F349334326317306299288277262
16°F365365365360352344334326310

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
97% of years
16°F or colder
64% 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
5,667
Cooling degree days, base 65°F
139
Growing degree days, base 40°F
3,972
Growing degree days, base 45°F
2,696
Growing degree days, base 50°F
1,709
Growing degree days, base 55°F
959
Growing degree days, base 60°F
433

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January85401
February70801
March67108
April534036
May3524145
June21513251
July8353436
August7352445
September17117298
October445083
November69905
December86201

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 Benton 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 USC00351877 (Corvallis Water Bureau). Public domain.