Lawrence County climate

Lawrence County Frost Dates and Growing Season

NOAA 1991-2020 normals for Waterloo, 12.6 km from Lawrence County, elevation 625 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Waterloo. 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 30 and the first fall freeze around October 15, a growing season of about 167 days.

Median at 36°F
last May 8, first October 5
Median at 32°F
last April 30, first October 15
Median at 28°F
last April 18, first October 25

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 24May 18May 15May 12May 8May 5May 2Apr 30Apr 25
32°FMay 16May 11May 7May 3Apr 30Apr 26Apr 23Apr 19Apr 15
28°FMay 6Apr 29Apr 24Apr 21Apr 18Apr 14Apr 11Apr 7Apr 3
24°FApr 20Apr 14Apr 10Apr 6Apr 4Apr 1Mar 30Mar 26Mar 21
20°FApr 5Apr 1Mar 29Mar 26Mar 23Mar 20Mar 17Mar 13Mar 4
16°FMar 27Mar 22Mar 18Mar 14Mar 10Mar 4Feb 28Feb 25Feb 15

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 23Sep 28Oct 1Oct 3Oct 5Oct 8Oct 10Oct 13Oct 18
32°FOct 3Oct 6Oct 9Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27
28°FOct 11Oct 16Oct 19Oct 22Oct 25Oct 28Oct 31Nov 2Nov 6
24°FOct 22Oct 28Oct 31Nov 2Nov 4Nov 7Nov 10Nov 14Nov 19
20°FNov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 22Nov 26Dec 2
16°FNov 11Nov 16Nov 20Nov 24Nov 28Dec 1Dec 6Dec 12Dec 22

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°F168162157153149145142137131
32°F186179175171167163159154148
28°F209202197192189185180174166
24°F233226221217213209205198191
20°F260252246241236232228223217
16°F292282274268263258253247238

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
5,275
Cooling degree days, base 65°F
873
Growing degree days, base 40°F
5,686
Growing degree days, base 45°F
4,422
Growing degree days, base 50°F
3,315
Growing degree days, base 55°F
2,358
Growing degree days, base 60°F
1,539

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06307
February87608
March722141
April3868154
May15860376
June23175602
July2281744
August5238697
September7998471
October36512174
November674033
December922011

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 12.6 km from Lawrence County. 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 USC00338810 (Waterloo). Public domain.