Miami County climate

Miami County Frost Dates and Growing Season

NOAA 1991-2020 normals for Piqua Wwtp, 8.7 km from Miami County, elevation 853 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Piqua 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 April 18 and the first fall freeze around October 23, a growing season of about 186 days.

Median at 36°F
last April 29, first October 13
Median at 32°F
last April 18, first October 23
Median at 28°F
last April 5, 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°FMay 14May 8May 5May 1Apr 29Apr 26Apr 23Apr 20Apr 16
32°FMay 5Apr 29Apr 24Apr 20Apr 18Apr 15Apr 12Apr 8Apr 5
28°FApr 20Apr 16Apr 12Apr 9Apr 5Apr 3Apr 1Mar 28Mar 23
24°FApr 10Apr 4Apr 1Mar 30Mar 27Mar 24Mar 21Mar 17Mar 11
20°FMar 31Mar 26Mar 22Mar 18Mar 16Mar 13Mar 9Mar 5Feb 28
16°FMar 21Mar 16Mar 12Mar 8Mar 5Mar 2Feb 28Feb 22Feb 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 30Oct 4Oct 8Oct 11Oct 13Oct 15Oct 18Oct 21Oct 25
32°FOct 9Oct 14Oct 17Oct 20Oct 23Oct 25Oct 29Oct 31Nov 4
28°FOct 20Oct 24Oct 29Nov 1Nov 3Nov 5Nov 9Nov 12Nov 18
24°FNov 1Nov 5Nov 9Nov 13Nov 16Nov 20Nov 23Nov 27Dec 2
20°FNov 11Nov 17Nov 21Nov 25Nov 29Dec 1Dec 5Dec 10Dec 18
16°FNov 21Nov 28Dec 2Dec 6Dec 10Dec 15Dec 19Dec 24Dec 29

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°F184177173169165161157152145
32°F206199194190186183178172164
28°F230223217213209206201197188
24°F257248244239234229225219213
20°F283274269263258254249243235
16°F308298291286281276269263254

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
5,406
Cooling degree days, base 65°F
953
Growing degree days, base 40°F
5,789
Growing degree days, base 45°F
4,549
Growing degree days, base 50°F
3,450
Growing degree days, base 55°F
2,482
Growing degree days, base 60°F
1,645

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,13802
February92308
March741243
April3819159
May13077417
June14198633
July3294756
August5238697
September71117497
October34317192
November658140
December1,00005

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 8.7 km from Miami County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00336650 (Piqua Wwtp). Public domain.