Algonac climate

Algonac Frost Dates and Growing Season

NOAA 1991-2020 normals for Algonac Wwtp, 1 km from Algonac, elevation 580 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Algonac 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 3 and the first fall freeze around October 18, a growing season of about 167 days.

Median at 36°F
last May 18, first October 6
Median at 32°F
last May 3, first October 18
Median at 28°F
last April 22, first October 31

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 5May 30May 25May 21May 18May 13May 8May 4Apr 30
32°FMay 23May 16May 11May 6May 3Apr 30Apr 27Apr 24Apr 20
28°FMay 8May 1Apr 27Apr 24Apr 22Apr 20Apr 17Apr 14Apr 8
24°FApr 22Apr 19Apr 16Apr 13Apr 10Apr 7Apr 4Apr 2Mar 29
20°FApr 14Apr 8Apr 4Apr 2Mar 31Mar 29Mar 25Mar 20Mar 15
16°FApr 1Mar 29Mar 26Mar 22Mar 19Mar 16Mar 14Mar 11Mar 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 23Sep 28Oct 1Oct 3Oct 6Oct 8Oct 11Oct 15Oct 20
32°FOct 4Oct 9Oct 12Oct 16Oct 18Oct 22Oct 25Oct 28Nov 1
28°FOct 18Oct 23Oct 26Oct 29Oct 31Nov 2Nov 5Nov 9Nov 12
24°FNov 1Nov 3Nov 6Nov 9Nov 11Nov 14Nov 16Nov 20Nov 24
20°FNov 8Nov 12Nov 16Nov 19Nov 22Nov 25Nov 28Dec 2Dec 9
16°FNov 18Nov 23Nov 28Dec 1Dec 5Dec 9Dec 14Dec 20Dec 25

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°F163155150145140135130124115
32°F185179176171167162156150141
28°F206201197193189185182177170
24°F233226222218214211207202196
20°F260252245241236232227223216
16°F284276271266261256251245239

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
6,551
Cooling degree days, base 65°F
643
Growing degree days, base 40°F
4,789
Growing degree days, base 45°F
3,696
Growing degree days, base 50°F
2,736
Growing degree days, base 55°F
1,902
Growing degree days, base 60°F
1,196

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,25100
February1,10300
March957110
April573057
May25625258
June58115508
July7241699
August15190640
September10364412
October4028140
November759012
December1,06801

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 1 km from Algonac. 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 USC00200106 (Algonac Wwtp). Public domain.