Decatur County climate

Decatur County Frost Dates and Growing Season

NOAA 1991-2020 normals for Oberlin, 6.4 km from Decatur County, elevation 2586 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Oberlin. 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 30 and the first fall freeze around October 11, a growing season of about 163 days.

Median at 36°F
last May 10, first October 2
Median at 32°F
last April 30, first October 11
Median at 28°F
last April 19, first October 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 24May 19May 15May 12May 10May 7May 4May 1Apr 27
32°FMay 14May 9May 5May 2Apr 30Apr 28Apr 25Apr 21Apr 16
28°FMay 4Apr 30Apr 26Apr 22Apr 19Apr 15Apr 12Apr 8Apr 4
24°FApr 22Apr 18Apr 13Apr 10Apr 6Apr 4Apr 1Mar 29Mar 22
20°FApr 15Apr 8Apr 4Apr 2Mar 31Mar 26Mar 22Mar 16Mar 10
16°FApr 6Apr 1Mar 27Mar 22Mar 17Mar 12Mar 9Mar 5Feb 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 18Sep 25Sep 28Oct 1Oct 2Oct 5Oct 7Oct 10Oct 14
32°FSep 27Oct 2Oct 5Oct 8Oct 11Oct 14Oct 16Oct 19Oct 23
28°FOct 7Oct 12Oct 15Oct 18Oct 20Oct 22Oct 25Oct 27Oct 31
24°FOct 17Oct 21Oct 24Oct 27Oct 29Nov 1Nov 3Nov 6Nov 12
20°FOct 23Oct 30Nov 1Nov 3Nov 6Nov 9Nov 13Nov 16Nov 22
16°FOct 31Nov 4Nov 8Nov 12Nov 15Nov 19Nov 22Nov 26Dec 1

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°F162156152149145141137132126
32°F182175171167163160156151144
28°F203197192187184179175171164
24°F224218213208204200196191184
20°F244236231226222217212207199
16°F265256250244239234229222214

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
5,807
Cooling degree days, base 65°F
1,137
Growing degree days, base 40°F
5,720
Growing degree days, base 45°F
4,522
Growing degree days, base 50°F
3,471
Growing degree days, base 55°F
2,556
Growing degree days, base 60°F
1,783

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12401
February93404
March737035
April4465119
May19554342
June23236663
July2385848
August6319778
September93127489
October39610167
November761024
December1,09101

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 6.4 km from Decatur 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 USC00145906 (Oberlin). Public domain.