Monroe climate

Monroe Frost Dates and Growing Season

NOAA 1991-2020 normals for Corvallis 10 Ssw, 11.9 km from Monroe, elevation 312 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Corvallis 10 Ssw. 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 11 and the first fall freeze around October 30, a growing season of about 203 days.

Median at 36°F
last May 11, first October 11
Median at 32°F
last April 11, first October 30
Median at 28°F
last February 28, first November 20

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 30May 23May 18May 14May 11May 6May 2Apr 29Apr 23
32°FMay 5Apr 29Apr 24Apr 17Apr 11Apr 5Mar 31Mar 24Mar 11
28°FMar 30Mar 21Mar 12Mar 5Feb 28Feb 25Feb 19Feb 12Jan 27
24°FFeb 28Feb 23Feb 16Feb 9Feb 1Jan 23Jan 9Dec 31Dec 14
20°FFeb 21Feb 4Jan 24Jan 13Jan 4Dec 29Dec 20Dec 12Dec 3
16°FFeb 2Jan 9Dec 31Dec 26Dec 22Dec 16Dec 12Dec 7Dec 3

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 28Oct 1Oct 4Oct 7Oct 11Oct 16Oct 20Oct 25Nov 1
32°FOct 8Oct 16Oct 21Oct 26Oct 30Nov 2Nov 8Nov 16Nov 25
28°FOct 27Nov 2Nov 9Nov 14Nov 20Nov 26Dec 2Dec 10Dec 22
24°FNov 11Nov 22Nov 29Dec 4Dec 11Dec 19Dec 27Jan 6Jan 27
20°FNov 26Dec 2Dec 8Dec 15Dec 23Dec 29Jan 5Jan 16Feb 4
16°FDec 1Dec 5Dec 10Dec 14Dec 18Dec 22Dec 28Jan 1Jan 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°F181172165159154148144138129
32°F241228218211203197190182172
28°F311292281272262256248239227
24°F365348337329318310303290274
20°F365365365365363353341331315
16°F365365365365365365365364347

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
90% of years
20°F or colder
54% of years
16°F or colder
22% 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
4,853
Cooling degree days, base 65°F
216
Growing degree days, base 40°F
4,699
Growing degree days, base 45°F
3,245
Growing degree days, base 50°F
2,088
Growing degree days, base 55°F
1,222
Growing degree days, base 60°F
603

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January75005
February62704
March583020
April465054
May3123169
June16321308
July3981507
August3781508
September11830362
October3731125
November609020
December77605

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 11.9 km from Monroe. 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 USW00004236 (Corvallis 10 Ssw). Public domain.