Owen County climate

Owen County Frost Dates and Growing Season

NOAA 1991-2020 normals for Williamstown, 27 km from Owen County, elevation 969 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Williamstown. 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 29, a growing season of about 199 days.

Median at 36°F
last April 24, first October 18
Median at 32°F
last April 11, first October 29
Median at 28°F
last March 31, first November 8

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 11May 5May 1Apr 27Apr 24Apr 20Apr 17Apr 14Apr 9
32°FApr 30Apr 22Apr 17Apr 15Apr 11Apr 8Apr 4Apr 1Mar 28
28°FApr 17Apr 10Apr 5Apr 2Mar 31Mar 29Mar 25Mar 20Mar 15
24°FApr 5Apr 1Mar 29Mar 25Mar 22Mar 18Mar 14Mar 10Mar 3
20°FMar 28Mar 22Mar 18Mar 14Mar 10Mar 6Mar 2Feb 26Feb 18
16°FMar 19Mar 12Mar 8Mar 4Feb 28Feb 24Feb 19Feb 11Feb 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°FOct 6Oct 11Oct 14Oct 16Oct 18Oct 21Oct 23Oct 26Oct 30
32°FOct 14Oct 20Oct 23Oct 26Oct 29Oct 31Nov 2Nov 6Nov 11
28°FOct 25Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15Nov 18Nov 25
24°FNov 4Nov 9Nov 13Nov 16Nov 20Nov 23Nov 28Dec 2Dec 10
20°FNov 14Nov 19Nov 24Nov 29Dec 2Dec 6Dec 10Dec 16Dec 22
16°FNov 25Dec 1Dec 6Dec 10Dec 15Dec 19Dec 23Dec 28Jan 4

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°F195190185181177173169164156
32°F219212207203199195189183175
28°F244237231226222218213208198
24°F269261255250245240234229221
20°F295286279273267262256250242
16°F321311303297291284279272263

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
4,392
Cooling degree days, base 65°F
1,276
Growing degree days, base 40°F
6,702
Growing degree days, base 45°F
5,340
Growing degree days, base 50°F
4,117
Growing degree days, base 55°F
3,027
Growing degree days, base 60°F
2,076

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January978012
February771014
March603274
April27424241
May80102488
June9249690
July0363828
August1327790
September32175593
October23432289
November552382
December857015

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 27 km from Owen 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 USC00158714 (Williamstown). Public domain.