Au Sable climate

Au Sable Frost Dates and Growing Season

NOAA 1991-2020 normals for E Tawas, 19.6 km from Au Sable, elevation 586 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for E Tawas. 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 8 and the first fall freeze around October 5, a growing season of about 148 days.

Median at 36°F
last May 23, first September 26
Median at 32°F
last May 8, first October 5
Median at 28°F
last April 28, first October 17

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 6Jun 1May 30May 26May 23May 19May 17May 12May 6
32°FMay 26May 19May 16May 12May 8May 5May 2Apr 30Apr 26
28°FMay 13May 8May 3Apr 30Apr 28Apr 25Apr 22Apr 18Apr 13
24°FApr 29Apr 24Apr 21Apr 18Apr 16Apr 13Apr 10Apr 6Apr 3
20°FApr 19Apr 15Apr 11Apr 8Apr 6Apr 3Apr 1Mar 30Mar 22
16°FApr 10Apr 5Apr 2Mar 31Mar 29Mar 26Mar 22Mar 18Mar 13

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 13Sep 18Sep 21Sep 24Sep 26Sep 29Oct 1Oct 3Oct 7
32°FSep 23Sep 28Oct 1Oct 3Oct 5Oct 7Oct 10Oct 13Oct 17
28°FOct 2Oct 7Oct 11Oct 14Oct 17Oct 20Oct 24Oct 28Nov 1
24°FOct 15Oct 22Oct 26Oct 29Nov 1Nov 3Nov 6Nov 10Nov 15
20°FOct 31Nov 4Nov 7Nov 11Nov 14Nov 17Nov 20Nov 24Nov 30
16°FNov 10Nov 15Nov 19Nov 23Nov 26Nov 29Dec 2Dec 5Dec 12

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°F146139133129125120116110104
32°F169161157152148144140135129
28°F192185180176171167163158150
24°F218211206202198194189184177
20°F241234229225221217213208202
16°F264256251246242238234230224

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
7,456
Cooling degree days, base 65°F
404
Growing degree days, base 40°F
4,059
Growing degree days, base 45°F
3,059
Growing degree days, base 50°F
2,192
Growing degree days, base 55°F
1,455
Growing degree days, base 60°F
849

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,34800
February1,18700
March1,05704
April684027
May34515182
June9875429
July25153594
August35120550
September17537321
October516381
November83106
December1,15500

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 19.6 km from Au Sable. 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 USC00202423 (E Tawas). Public domain.