Harbor Springs climate

Harbor Springs Frost Dates and Growing Season

NOAA 1991-2020 normals for Petoskey, 6.7 km from Harbor Springs, elevation 599 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Petoskey. 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 6 and the first fall freeze around October 20, a growing season of about 166 days.

Median at 36°F
last May 20, first October 5
Median at 32°F
last May 6, first October 20
Median at 28°F
last April 23, first November 3

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 29May 26May 23May 20May 16May 13May 9May 3
32°FMay 21May 16May 12May 9May 6May 3Apr 30Apr 28Apr 23
28°FMay 7May 2Apr 29Apr 26Apr 23Apr 20Apr 17Apr 13Apr 9
24°FApr 24Apr 20Apr 16Apr 14Apr 11Apr 8Apr 5Apr 3Mar 30
20°FApr 17Apr 11Apr 8Apr 5Apr 3Apr 1Mar 30Mar 25Mar 19
16°FApr 8Apr 5Apr 2Mar 31Mar 28Mar 23Mar 20Mar 16Mar 12

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 2Oct 5Oct 8Oct 12Oct 16Oct 21
32°FOct 2Oct 6Oct 11Oct 16Oct 20Oct 23Oct 27Oct 30Nov 4
28°FOct 18Oct 24Oct 28Nov 1Nov 3Nov 5Nov 9Nov 13Nov 18
24°FNov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 23Nov 26Dec 1
20°FNov 9Nov 15Nov 19Nov 22Nov 26Nov 29Dec 1Dec 6Dec 13
16°FNov 18Nov 24Nov 29Dec 1Dec 5Dec 9Dec 14Dec 19Dec 24

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°F159152147143139136131126120
32°F186179175170166161156151143
28°F212206201197193189184179173
24°F238231225221217213209203197
20°F258249244240235231227222215
16°F275267262257252248243237231

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
7,788
Cooling degree days, base 65°F
316
Growing degree days, base 40°F
3,785
Growing degree days, base 45°F
2,816
Growing degree days, base 50°F
1,981
Growing degree days, base 55°F
1,275
Growing degree days, base 60°F
711

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,35800
February1,23100
March1,13504
April753023
May4219136
June14749356
July45115535
August45101521
September18438314
October512484
November82108
December1,13800

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 6.7 km from Harbor Springs. 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 USC00206507 (Petoskey). Public domain.