Harrison climate

Harrison Frost Dates and Growing Season

NOAA 1991-2020 normals for Carbondale Southern Il AP, 7.9 km from Harrison, elevation 406 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Carbondale Southern Il 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 9 and the first fall freeze around October 22, a growing season of about 195 days.

Median at 36°F
last April 21, first October 12
Median at 32°F
last April 9, first October 22
Median at 28°F
last March 30, first November 1

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 6May 1Apr 27Apr 24Apr 21Apr 18Apr 15Apr 11Apr 6
32°FApr 25Apr 20Apr 16Apr 12Apr 9Apr 6Apr 3Mar 31Mar 24
28°FApr 14Apr 8Apr 4Apr 1Mar 30Mar 26Mar 22Mar 18Mar 11
24°FApr 3Mar 28Mar 23Mar 19Mar 16Mar 13Mar 8Mar 4Feb 27
20°FMar 21Mar 16Mar 12Mar 8Mar 4Mar 1Feb 25Feb 19Feb 10
16°FMar 13Mar 6Mar 1Feb 26Feb 22Feb 17Feb 11Feb 5Jan 30

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 7Oct 10Oct 12Oct 15Oct 17Oct 19Oct 23
32°FOct 8Oct 13Oct 17Oct 19Oct 22Oct 24Oct 26Oct 29Nov 1
28°FOct 21Oct 25Oct 28Oct 31Nov 1Nov 3Nov 6Nov 11Nov 17
24°FNov 1Nov 4Nov 7Nov 10Nov 13Nov 17Nov 22Nov 28Dec 4
20°FNov 9Nov 15Nov 18Nov 22Nov 26Nov 30Dec 4Dec 9Dec 17
16°FNov 19Nov 25Nov 30Dec 4Dec 8Dec 13Dec 19Dec 24Jan 2

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°F192186181176173169164159152
32°F213207202199195192187182175
28°F239231226221217212208202195
24°F267258252247242236232227219
20°F294285278272267262257251240
16°F321309301295290285279272263

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
4,460
Cooling degree days, base 65°F
1,370
Growing degree days, base 40°F
6,736
Growing degree days, base 45°F
5,375
Growing degree days, base 50°F
4,161
Growing degree days, base 55°F
3,090
Growing degree days, base 60°F
2,160

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January984010
February770019
March577482
April27524239
May81118503
June4302748
July0401866
August1342806
September49146548
October26731260
November584265
December870016

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 7.9 km from Harrison. 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 USW00093810 (Carbondale Southern Il AP). Public domain.