Louisville climate

Louisville Frost Dates and Growing Season

NOAA 1991-2020 normals for Louisville 1 E, 2.2 km from Louisville, elevation 322 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Louisville 1 E. 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 25 and the first fall freeze around November 7, a growing season of about 227 days.

Median at 36°F
last April 6, first October 29
Median at 32°F
last March 25, first November 7
Median at 28°F
last March 12, first November 20

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 20Apr 16Apr 12Apr 9Apr 6Apr 3Mar 31Mar 27Mar 21
32°FApr 9Apr 4Mar 31Mar 28Mar 25Mar 21Mar 18Mar 13Mar 6
28°FMar 29Mar 25Mar 20Mar 16Mar 12Mar 8Mar 2Feb 26Feb 17
24°FMar 19Mar 11Mar 5Mar 1Feb 24Feb 17Feb 10Feb 2Jan 25
20°FMar 6Mar 1Feb 19Feb 11Feb 4Jan 30Jan 22Jan 15Jan 2
16°FFeb 26Feb 10Feb 4Jan 30Jan 26Jan 19Jan 12Jan 6Dec 27

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 16Oct 21Oct 24Oct 27Oct 29Nov 1Nov 3Nov 7Nov 11
32°FOct 25Oct 30Nov 2Nov 4Nov 7Nov 10Nov 15Nov 19Nov 26
28°FNov 4Nov 8Nov 12Nov 16Nov 20Nov 25Dec 1Dec 5Dec 14
24°FNov 16Nov 24Dec 1Dec 3Dec 8Dec 15Dec 25Jan 3Jan 13
20°FDec 1Dec 8Dec 16Dec 24Jan 1Jan 5Jan 11Jan 17Jan 31
16°FDec 14Dec 23Jan 1Jan 6Jan 11Jan 15Jan 23Jan 30Feb 8

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°F227219213208204200196192185
32°F256245239232227223218212205
28°F288275267261255250244237228
24°F327315306299292284276268256
20°F365348339332325316308301286
16°F365365365365359347337329315

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
87% of years
16°F or colder
52% 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
2,510
Cooling degree days, base 65°F
2,007
Growing degree days, base 40°F
8,726
Growing degree days, base 45°F
7,072
Growing degree days, base 50°F
5,558
Growing degree days, base 55°F
4,204
Growing degree days, base 60°F
3,014

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January604164
February454284
March31315216
April12462393
May22211654
June0387837
July0490955
August0454919
September7289732
October10682445
November33912176
December542283

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 2.2 km from Louisville. 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 USC00095314 (Louisville 1 E). Public domain.