Mounds climate

Mounds Frost Dates and Growing Season

NOAA 1991-2020 normals for Cairo 3N, 8.1 km from Mounds, elevation 313 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cairo 3N. 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 2 and the first fall freeze around October 31, a growing season of about 211 days.

Median at 36°F
last April 12, first October 20
Median at 32°F
last April 2, first October 31
Median at 28°F
last March 24, first November 10

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°FApr 28Apr 22Apr 19Apr 15Apr 12Apr 10Apr 7Apr 3Mar 31
32°FApr 17Apr 11Apr 8Apr 5Apr 2Mar 31Mar 28Mar 24Mar 19
28°FApr 8Apr 3Mar 31Mar 28Mar 24Mar 21Mar 18Mar 14Mar 7
24°FMar 29Mar 24Mar 20Mar 17Mar 13Mar 9Mar 4Feb 28Feb 23
20°FMar 20Mar 14Mar 9Mar 5Mar 2Feb 27Feb 22Feb 16Feb 8
16°FMar 13Mar 6Mar 1Feb 26Feb 20Feb 15Feb 9Feb 3Jan 28

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 8Oct 12Oct 16Oct 19Oct 20Oct 23Oct 26Oct 29Nov 1
32°FOct 18Oct 22Oct 26Oct 28Oct 31Nov 2Nov 5Nov 9Nov 13
28°FOct 29Nov 1Nov 3Nov 6Nov 10Nov 12Nov 16Nov 20Nov 28
24°FNov 4Nov 10Nov 13Nov 17Nov 21Nov 25Nov 29Dec 3Dec 10
20°FNov 14Nov 20Nov 26Nov 29Dec 2Dec 7Dec 13Dec 19Dec 26
16°FNov 25Dec 1Dec 6Dec 11Dec 18Dec 23Dec 28Jan 1Jan 11

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°F208202198194190186182176169
32°F229222218214211207203197191
28°F252244239234230226222217210
24°F278269261257252247243237229
20°F306295288281276272265258249
16°F331321313306301295287280271

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
99% 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
4,075
Cooling degree days, base 65°F
1,592
Growing degree days, base 40°F
7,212
Growing degree days, base 45°F
5,802
Growing degree days, base 50°F
4,539
Growing degree days, base 55°F
3,416
Growing degree days, base 60°F
2,432

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January939011
February732017
March530699
April22738288
May52145558
June2332780
July0439904
August1393857
September27196619
October21740306
November523383
December825018

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 8.1 km from Mounds. 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 USW00093809 (Cairo 3N). Public domain.