Wythe County climate

Wythe County Frost Dates and Growing Season

NOAA 1991-2020 normals for Wytheville, 5 km from Wythe County, elevation 2458 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wytheville. 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 25 and the first fall freeze around October 18, a growing season of about 174 days.

Median at 36°F
last May 7, first October 8
Median at 32°F
last April 25, first October 18
Median at 28°F
last April 10, first October 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°FMay 25May 19May 15May 11May 7May 4May 1Apr 27Apr 22
32°FMay 16May 9May 4Apr 30Apr 25Apr 22Apr 18Apr 15Apr 10
28°FMay 3Apr 22Apr 16Apr 13Apr 10Apr 6Apr 3Mar 31Mar 25
24°FApr 11Apr 5Apr 1Mar 30Mar 27Mar 24Mar 20Mar 16Mar 10
20°FMar 30Mar 25Mar 20Mar 17Mar 13Mar 10Mar 6Mar 2Feb 22
16°FMar 20Mar 15Mar 10Mar 5Mar 1Feb 26Feb 18Feb 12Feb 3

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 30Oct 3Oct 5Oct 8Oct 11Oct 14Oct 17Oct 22
32°FOct 5Oct 9Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Nov 1
28°FOct 13Oct 17Oct 21Oct 24Oct 27Oct 30Nov 1Nov 4Nov 9
24°FOct 22Oct 27Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15Nov 22
20°FNov 1Nov 6Nov 10Nov 13Nov 16Nov 20Nov 25Nov 30Dec 6
16°FNov 11Nov 16Nov 21Nov 28Dec 2Dec 6Dec 13Dec 20Dec 30

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°F174167161157153149144139132
32°F195188183178174170165159152
28°F219212207203198193188183174
24°F247238232227222218213208200
20°F279267259253248243237232223
16°F312301292284278271264257248

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
5,118
Cooling degree days, base 65°F
639
Growing degree days, base 40°F
5,434
Growing degree days, base 45°F
4,145
Growing degree days, base 50°F
3,026
Growing degree days, base 55°F
2,072
Growing degree days, base 60°F
1,274

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January99704
February81907
March695036
April3983135
May17636337
June32122540
July6213673
August8183640
September8473441
October3608167
November653036
December89309

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 5 km from Wythe 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 USC00449301 (Wytheville). Public domain.