Ionia County climate

Ionia County Frost Dates and Growing Season

NOAA 1991-2020 normals for Ionia 2SSW, 0.9 km from Ionia County, elevation 805 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ionia 2SSW. 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 12, a growing season of about 161 days.

Median at 36°F
last May 16, first October 1
Median at 32°F
last May 3, first October 12
Median at 28°F
last April 22, first October 27

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 1May 27May 23May 19May 16May 12May 8May 4Apr 30
32°FMay 21May 15May 10May 6May 3Apr 30Apr 27Apr 23Apr 17
28°FMay 9May 3Apr 29Apr 25Apr 22Apr 19Apr 16Apr 12Apr 7
24°FApr 25Apr 20Apr 17Apr 14Apr 10Apr 7Apr 4Apr 2Mar 28
20°FApr 15Apr 9Apr 6Apr 3Apr 1Mar 29Mar 25Mar 21Mar 16
16°FApr 4Mar 31Mar 28Mar 24Mar 21Mar 18Mar 16Mar 12Mar 7

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 18Sep 23Sep 27Sep 29Oct 1Oct 4Oct 7Oct 10Oct 15
32°FSep 29Oct 3Oct 6Oct 9Oct 12Oct 16Oct 19Oct 22Oct 27
28°FOct 7Oct 15Oct 20Oct 23Oct 27Oct 30Nov 1Nov 5Nov 10
24°FOct 25Oct 31Nov 2Nov 5Nov 8Nov 12Nov 15Nov 19Nov 26
20°FNov 6Nov 11Nov 15Nov 19Nov 22Nov 26Nov 29Dec 2Dec 9
16°FNov 15Nov 22Nov 26Nov 30Dec 2Dec 5Dec 10Dec 16Dec 22

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°F159152147143139135131125119
32°F183176170165161157152146139
28°F207201196191186182176170162
24°F235227222217212208203198191
20°F257250245241236231227222215
16°F279271265260255251246241234

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
7,039
Cooling degree days, base 65°F
546
Growing degree days, base 40°F
4,501
Growing degree days, base 45°F
3,448
Growing degree days, base 50°F
2,525
Growing degree days, base 55°F
1,728
Growing degree days, base 60°F
1,059

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,32500
February1,14900
March983115
April598360
May27033257
June62122511
July16189639
August27145583
September16250346
October4875102
November812012
December1,14801

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 0.9 km from Ionia 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 USC00204078 (Ionia 2SSW). Public domain.