Hamilton County climate

Hamilton County Frost Dates and Growing Season

NOAA 1991-2020 normals for Mcleansboro, 0.4 km from Hamilton County, elevation 446 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mcleansboro. 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 11 and the first fall freeze around October 21, a growing season of about 190 days.

Median at 36°F
last April 22, first October 11
Median at 32°F
last April 11, first October 21
Median at 28°F
last April 1, first October 30

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 8May 2Apr 29Apr 25Apr 22Apr 19Apr 15Apr 11Apr 6
32°FApr 26Apr 22Apr 18Apr 14Apr 11Apr 8Apr 4Mar 31Mar 27
28°FApr 17Apr 12Apr 7Apr 4Apr 1Mar 30Mar 26Mar 21Mar 16
24°FApr 7Apr 1Mar 29Mar 25Mar 22Mar 18Mar 15Mar 11Mar 6
20°FMar 29Mar 23Mar 18Mar 15Mar 12Mar 8Mar 5Mar 2Feb 25
16°FMar 19Mar 14Mar 9Mar 6Mar 3Mar 1Feb 26Feb 20Feb 12

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 28Oct 2Oct 5Oct 8Oct 11Oct 13Oct 16Oct 20Oct 23
32°FOct 6Oct 12Oct 15Oct 18Oct 21Oct 23Oct 26Oct 28Nov 1
28°FOct 17Oct 22Oct 24Oct 27Oct 30Nov 1Nov 3Nov 6Nov 10
24°FOct 26Oct 31Nov 2Nov 5Nov 7Nov 10Nov 14Nov 18Nov 23
20°FNov 4Nov 8Nov 11Nov 15Nov 18Nov 22Nov 26Dec 1Dec 7
16°FNov 11Nov 16Nov 21Nov 25Nov 30Dec 3Dec 7Dec 15Dec 21

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°F191184179174170166163158151
32°F211204200194190187182176169
28°F229223217213209205201195188
24°F252245239235230226221215209
20°F276267262257252246241235228
16°F302293285279273267261254246

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
4,746
Cooling degree days, base 65°F
1,306
Growing degree days, base 40°F
6,535
Growing degree days, base 45°F
5,215
Growing degree days, base 50°F
4,039
Growing degree days, base 55°F
2,992
Growing degree days, base 60°F
2,077

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,03507
February83308
March624470
April30219215
May82106491
June7277720
July0389854
August2329792
September46156560
October27925252
November618260
December917011

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 0.4 km from Hamilton 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 USC00115515 (Mcleansboro). Public domain.