Mitchell County climate

Mitchell County Frost Dates and Growing Season

NOAA 1991-2020 normals for Osage, 8.7 km from Mitchell County, elevation 1170 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Osage. 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 9, a growing season of about 163 days.

Median at 36°F
last May 8, first September 30
Median at 32°F
last April 30, first October 9
Median at 28°F
last April 17, 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 21May 16May 13May 10May 8May 6May 3May 1Apr 25
32°FMay 12May 7May 4May 2Apr 30Apr 26Apr 22Apr 19Apr 14
28°FApr 30Apr 27Apr 23Apr 20Apr 17Apr 14Apr 10Apr 7Apr 3
24°FApr 22Apr 17Apr 13Apr 9Apr 7Apr 4Apr 2Mar 31Mar 24
20°FApr 14Apr 8Apr 5Apr 2Mar 31Mar 28Mar 24Mar 20Mar 14
16°FApr 7Apr 2Mar 31Mar 27Mar 23Mar 20Mar 16Mar 13Mar 8

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 17Sep 21Sep 25Sep 27Sep 30Oct 2Oct 4Oct 8Oct 12
32°FSep 25Sep 29Oct 3Oct 6Oct 9Oct 11Oct 14Oct 17Oct 21
28°FOct 5Oct 10Oct 14Oct 17Oct 20Oct 22Oct 24Oct 27Nov 1
24°FOct 17Oct 22Oct 24Oct 27Oct 30Nov 1Nov 3Nov 7Nov 12
20°FOct 27Oct 31Nov 2Nov 5Nov 7Nov 10Nov 13Nov 16Nov 22
16°FNov 2Nov 6Nov 9Nov 11Nov 14Nov 18Nov 21Nov 25Nov 30

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°F161154150147144140137132126
32°F182175171167163159155150144
28°F204198193189185181176172164
24°F222216211208204201197192186
20°F242236230225221217213209202
16°F257250244240236232228223216

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
7,745
Cooling degree days, base 65°F
593
Growing degree days, base 40°F
4,562
Growing degree days, base 45°F
3,538
Growing degree days, base 50°F
2,618
Growing degree days, base 55°F
1,818
Growing degree days, base 60°F
1,138

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,55900
February1,28500
March1,026011
April586364
May25633271
June45136542
July9212668
August23148591
September15655359
October5146104
November93509
December1,35200

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 8.7 km from Mitchell 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 USC00136305 (Osage). Public domain.