Columbia County climate

Columbia County Frost Dates and Growing Season

NOAA 1991-2020 normals for Vernonia #2, 11.8 km from Columbia County, elevation 625 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Vernonia #2. 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 8 and the first fall freeze around October 1, a growing season of about 144 days.

Median at 32°F
last May 8, first October 1
Median at 28°F
last April 12, first October 21

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°F–––––––––
32°FMay 29May 23May 17May 12May 8May 2Apr 30Apr 26Apr 18
28°FMay 7May 1Apr 26Apr 19Apr 12Apr 7Apr 1Mar 25Mar 14
24°FApr 5Mar 26Mar 18Mar 12Mar 5Feb 28Feb 23Feb 18Feb 2
20°FMar 6Feb 28Feb 23Feb 18Feb 12Feb 1Jan 17Jan 6Dec 18
16°FFeb 25Feb 18Feb 9Jan 29Jan 14Jan 2Dec 26Dec 12Dec 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°F–––––––––
32°FSep 11Sep 18Sep 24Sep 28Oct 1Oct 6Oct 10Oct 18Oct 28
28°FSep 28Oct 3Oct 8Oct 15Oct 21Oct 26Nov 1Nov 9Nov 19
24°FOct 14Oct 25Nov 1Nov 9Nov 15Nov 23Nov 28Dec 6Dec 20
20°FNov 4Nov 14Nov 23Nov 29Dec 5Dec 14Dec 24Jan 1Jan 20
16°FNov 13Nov 27Dec 3Dec 9Dec 17Dec 27Jan 2Jan 22Feb 14

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°F1251151071009487797260
32°F178166157151144138131124114
28°F230217207199191185178168157
24°F298283272263253242232224212
20°F354336324315307299290280265
16°F365365364354343334324311302

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
95% of years
16°F or colder
69% 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
5,772
Cooling degree days, base 65°F
84
Growing degree days, base 40°F
3,756
Growing degree days, base 45°F
2,461
Growing degree days, base 50°F
1,476
Growing degree days, base 55°F
764
Growing degree days, base 60°F
310

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January81701
February69601
March66508
April537033
May3772127
June2448219
July11933380
August10933389
September2188244
October470067
November67808
December84301

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 Columbia 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 USC00358884 (Vernonia #2). Public domain.