Ackerman climate

Ackerman Frost Dates and Growing Season

NOAA 1991-2020 normals for Louisville, 21.6 km from Ackerman, elevation 581 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Louisville. 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 March 21 and the first fall freeze around November 13, a growing season of about 235 days.

Median at 36°F
last April 4, first November 1
Median at 32°F
last March 21, first November 13
Median at 28°F
last March 7, first November 27

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 21Apr 15Apr 10Apr 7Apr 4Apr 1Mar 29Mar 24Mar 17
32°FApr 9Apr 3Mar 30Mar 25Mar 21Mar 17Mar 14Mar 9Mar 1
28°FMar 24Mar 18Mar 15Mar 11Mar 7Mar 2Feb 26Feb 21Feb 12
24°FMar 15Mar 9Mar 2Feb 26Feb 20Feb 14Feb 8Feb 2Jan 25
20°FMar 7Feb 27Feb 15Feb 7Feb 2Jan 30Jan 23Jan 15Jan 3
16°FFeb 21Feb 8Feb 2Jan 30Jan 25Jan 19Jan 13Jan 6Dec 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°FOct 21Oct 25Oct 28Oct 31Nov 1Nov 4Nov 8Nov 11Nov 17
32°FOct 30Nov 2Nov 6Nov 9Nov 13Nov 17Nov 21Nov 25Dec 1
28°FNov 6Nov 12Nov 18Nov 22Nov 27Dec 1Dec 3Dec 8Dec 18
24°FNov 18Nov 26Dec 1Dec 4Dec 9Dec 16Dec 26Jan 1Jan 10
20°FDec 2Dec 10Dec 18Dec 25Dec 31Jan 3Jan 10Jan 17Jan 27
16°FDec 12Dec 23Dec 29Jan 2Jan 7Jan 13Jan 17Jan 24Feb 1

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°F233226220216211207203197191
32°F261252246240235229223218209
28°F291283276270264258252245236
24°F328318307300295289282275263
20°F365347337332326318309301291
16°F365365365362354346337331317

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
99% of years
20°F or colder
89% of years
16°F or colder
61% 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
2,631
Cooling degree days, base 65°F
2,114
Growing degree days, base 40°F
8,768
Growing degree days, base 45°F
7,145
Growing degree days, base 50°F
5,655
Growing degree days, base 55°F
4,313
Growing degree days, base 60°F
3,130

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January639263
February479387
March30718228
April13170397
May22222665
June0396846
July0497962
August0480945
September7311754
October11298458
November35813171
December578480

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 21.6 km from Ackerman. 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 USC00225247 (Louisville). Public domain.