Corunna climate

Corunna Frost Dates and Growing Season

NOAA 1991-2020 normals for Owosso Wwtp, 6.3 km from Corunna, elevation 730 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Owosso Wwtp. 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 1 and the first fall freeze around October 15, a growing season of about 164 days.

Median at 36°F
last May 11, first October 4
Median at 32°F
last May 1, first October 15
Median at 28°F
last April 20, first October 28

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 28May 23May 19May 15May 11May 8May 5May 1Apr 28
32°FMay 17May 11May 7May 4May 1Apr 29Apr 26Apr 22Apr 17
28°FMay 5Apr 30Apr 28Apr 23Apr 20Apr 18Apr 14Apr 10Apr 5
24°FApr 24Apr 19Apr 15Apr 11Apr 8Apr 5Apr 2Mar 31Mar 25
20°FApr 11Apr 6Apr 3Apr 1Mar 30Mar 27Mar 23Mar 19Mar 15
16°FApr 1Mar 30Mar 27Mar 23Mar 20Mar 17Mar 14Mar 10Mar 5

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 22Sep 26Sep 30Oct 1Oct 4Oct 6Oct 8Oct 12Oct 16
32°FOct 1Oct 5Oct 8Oct 12Oct 15Oct 17Oct 20Oct 24Oct 30
28°FOct 12Oct 17Oct 21Oct 25Oct 28Oct 31Nov 2Nov 5Nov 11
24°FOct 25Oct 31Nov 2Nov 5Nov 8Nov 11Nov 16Nov 20Nov 25
20°FNov 5Nov 10Nov 14Nov 18Nov 22Nov 26Nov 29Dec 3Dec 9
16°FNov 16Nov 22Nov 27Nov 30Dec 2Dec 6Dec 10Dec 16Dec 23

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°F162156152148144140135131124
32°F185178173168164160156152146
28°F209203197192188182178172165
24°F236229223218214209204200192
20°F260253247243239233228222214
16°F282274267263258254248244235

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
6,868
Cooling degree days, base 65°F
578
Growing degree days, base 40°F
4,607
Growing degree days, base 45°F
3,536
Growing degree days, base 50°F
2,599
Growing degree days, base 55°F
1,790
Growing degree days, base 60°F
1,107

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,30200
February1,12801
March976114
April588362
May27036258
June59120512
July15194645
August24156597
September14461374
October4627118
November785017
December1,11602

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 6.3 km from Corunna. 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 USC00206300 (Owosso Wwtp). Public domain.