Boone County climate

Boone County Frost Dates and Growing Season

NOAA 1991-2020 normals for Cincinnati Northern Ky AP, 9.5 km from Boone County, elevation 869 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cincinnati Northern Ky AP. 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 25, a growing season of about 188 days.

Median at 36°F
last April 30, first October 15
Median at 32°F
last April 18, first October 25
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 17May 10May 6May 2Apr 30Apr 26Apr 23Apr 19Apr 14
32°FMay 7Apr 30Apr 26Apr 22Apr 18Apr 15Apr 12Apr 8Apr 3
28°FApr 23Apr 17Apr 12Apr 9Apr 5Apr 2Mar 31Mar 27Mar 21
24°FApr 10Apr 3Mar 31Mar 28Mar 25Mar 22Mar 19Mar 15Mar 7
20°FApr 1Mar 26Mar 21Mar 18Mar 14Mar 11Mar 6Mar 2Feb 22
16°FMar 22Mar 17Mar 12Mar 8Mar 4Feb 28Feb 23Feb 16Feb 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°FOct 2Oct 7Oct 10Oct 13Oct 15Oct 18Oct 20Oct 23Oct 26
32°FOct 12Oct 17Oct 20Oct 23Oct 25Oct 28Oct 30Nov 1Nov 5
28°FOct 22Oct 27Oct 30Nov 1Nov 3Nov 5Nov 8Nov 11Nov 16
24°FNov 1Nov 4Nov 7Nov 11Nov 13Nov 16Nov 19Nov 23Nov 30
20°FNov 8Nov 13Nov 17Nov 21Nov 25Nov 30Dec 3Dec 8Dec 16
16°FNov 18Nov 26Nov 30Dec 4Dec 8Dec 13Dec 19Dec 24Dec 31

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°F189182178174169165161156149
32°F209202197192188184179173166
28°F234227221216212209204198190
24°F259249243238233228225219212
20°F285274268262257252246240231
16°F309300292287280274268261251

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
4,892
Cooling degree days, base 65°F
1,160
Growing degree days, base 40°F
6,288
Growing degree days, base 45°F
4,979
Growing degree days, base 50°F
3,814
Growing degree days, base 55°F
2,788
Growing degree days, base 60°F
1,902

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,04308
February847012
March664362
April32816200
May11890441
June13233670
July1340804
August2309772
September53146544
October29623232
November617156
December911013

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 9.5 km from Boone 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 USW00093814 (Cincinnati Northern Ky AP). Public domain.