Columbia County climate

Columbia County Frost Dates and Growing Season

NOAA 1991-2020 normals for Dayton 1 Wsw, 7.5 km from Columbia County, elevation 1557 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dayton 1 Wsw. 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 28 and the first fall freeze around October 13, a growing season of about 168 days.

Median at 36°F
last May 12, first October 1
Median at 32°F
last April 28, first October 13
Median at 28°F
last April 6, first October 25

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 3May 27May 21May 16May 12May 9May 6May 3Apr 28
32°FMay 14May 8May 4Apr 30Apr 28Apr 25Apr 22Apr 17Apr 11
28°FApr 28Apr 20Apr 15Apr 10Apr 6Apr 1Mar 28Mar 23Mar 15
24°FApr 3Mar 28Mar 22Mar 16Mar 11Mar 7Mar 4Feb 28Feb 19
20°FMar 14Mar 7Mar 2Feb 26Feb 22Feb 17Feb 11Feb 3Jan 20
16°FMar 3Feb 25Feb 19Feb 12Feb 5Jan 30Jan 20Jan 10Dec 28

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 14Sep 22Sep 26Sep 29Oct 1Oct 4Oct 7Oct 10Oct 15
32°FSep 30Oct 4Oct 7Oct 10Oct 13Oct 16Oct 20Oct 24Oct 29
28°FOct 9Oct 14Oct 18Oct 22Oct 25Oct 28Nov 1Nov 5Nov 12
24°FOct 18Oct 25Oct 29Nov 1Nov 6Nov 11Nov 17Nov 23Nov 30
20°FOct 26Nov 3Nov 11Nov 19Nov 24Nov 29Dec 4Dec 9Dec 19
16°FNov 9Nov 20Nov 28Dec 3Dec 9Dec 15Dec 22Dec 30Jan 9

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°F161154149143138133128121112
32°F190182178173168164160155147
28°F231219212207203197191184176
24°F269259249244239233227220209
20°F316302292283275269261250240
16°F350336324315308301292282268

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
97% 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
5,622
Cooling degree days, base 65°F
564
Growing degree days, base 40°F
4,823
Growing degree days, base 45°F
3,572
Growing degree days, base 50°F
2,541
Growing degree days, base 55°F
1,711
Growing degree days, base 60°F
1,053

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January96302
February77803
March668019
April468176
May26220245
June12070408
July21215659
August29198635
September14359379
October4532102
November746011
December97302

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 7.5 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 USC00452030 (Dayton 1 Wsw). Public domain.