Morgan County climate

Morgan County Frost Dates and Growing Season

NOAA 1991-2020 normals for Martinsville 2 Sw, 8.7 km from Morgan County, elevation 592 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Martinsville 2 Sw. 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 24 and the first fall freeze around October 15, a growing season of about 173 days.

Median at 36°F
last May 4, first October 6
Median at 32°F
last April 24, first October 15
Median at 28°F
last April 12, first October 26

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 21May 15May 11May 7May 4May 1Apr 28Apr 24Apr 20
32°FMay 11May 5May 1Apr 28Apr 24Apr 21Apr 17Apr 14Apr 10
28°FApr 30Apr 23Apr 19Apr 15Apr 12Apr 8Apr 6Apr 3Mar 29
24°FApr 14Apr 8Apr 4Apr 2Mar 31Mar 29Mar 25Mar 21Mar 14
20°FApr 3Mar 30Mar 26Mar 22Mar 19Mar 16Mar 12Mar 8Feb 28
16°FMar 25Mar 20Mar 16Mar 13Mar 9Mar 6Mar 2Feb 25Feb 16

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 24Sep 29Oct 1Oct 4Oct 6Oct 8Oct 11Oct 14Oct 19
32°FOct 2Oct 7Oct 10Oct 13Oct 15Oct 18Oct 21Oct 24Oct 29
28°FOct 12Oct 17Oct 21Oct 23Oct 26Oct 28Oct 31Nov 2Nov 7
24°FOct 23Oct 27Oct 30Nov 1Nov 5Nov 7Nov 11Nov 15Nov 24
20°FNov 1Nov 6Nov 10Nov 14Nov 18Nov 23Nov 27Dec 2Dec 8
16°FNov 13Nov 20Nov 25Nov 28Dec 1Dec 5Dec 11Dec 17Dec 23

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°F173166161157154150146140132
32°F191187181177173168164159152
28°F214207202198194190185180171
24°F241233227222217213209203196
20°F270261255250244239233227221
16°F295285278273269263257251242

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
5,647
Cooling degree days, base 65°F
837
Growing degree days, base 40°F
5,536
Growing degree days, base 45°F
4,319
Growing degree days, base 50°F
3,244
Growing degree days, base 55°F
2,301
Growing degree days, base 60°F
1,492

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,15904
February95105
March767139
April4138142
May16459370
June24180606
July4261722
August8221679
September8795462
October37611171
November692038
December1,00407

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 8.7 km from Morgan 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 USC00125407 (Martinsville 2 Sw). Public domain.