Chilhowie climate

Chilhowie Frost Dates and Growing Season

NOAA 1991-2020 normals for Saltville 1N, 12.8 km from Chilhowie, elevation 1733 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Saltville 1N. 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 23 and the first fall freeze around October 20, a growing season of about 178 days.

Median at 36°F
last May 5, first October 11
Median at 32°F
last April 23, first October 20
Median at 28°F
last April 9, first October 29

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 22May 15May 11May 8May 5May 1Apr 30Apr 26Apr 21
32°FMay 10May 4Apr 30Apr 27Apr 23Apr 21Apr 18Apr 15Apr 10
28°FApr 23Apr 19Apr 16Apr 12Apr 9Apr 6Apr 3Mar 31Mar 25
24°FApr 12Apr 6Apr 2Mar 31Mar 27Mar 24Mar 21Mar 18Mar 13
20°FMar 28Mar 23Mar 19Mar 16Mar 13Mar 10Mar 5Mar 1Feb 23
16°FMar 19Mar 14Mar 8Mar 3Feb 28Feb 25Feb 19Feb 13Feb 5

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 30Oct 4Oct 7Oct 9Oct 11Oct 14Oct 17Oct 20Oct 25
32°FOct 8Oct 12Oct 15Oct 17Oct 20Oct 23Oct 25Oct 29Nov 1
28°FOct 14Oct 19Oct 23Oct 26Oct 29Oct 31Nov 2Nov 5Nov 9
24°FOct 24Oct 28Nov 1Nov 3Nov 5Nov 9Nov 12Nov 16Nov 22
20°FNov 2Nov 7Nov 12Nov 15Nov 19Nov 23Nov 27Dec 1Dec 8
16°FNov 15Nov 21Nov 27Dec 1Dec 2Dec 7Dec 13Dec 20Dec 29

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°F177170166162159155151146138
32°F197190186182178174170165158
28°F221214209205201197192187181
24°F246239233228224220215210203
20°F277268261256251246240234227
16°F310300293286279273267260251

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
4,818
Cooling degree days, base 65°F
796
Growing degree days, base 40°F
5,802
Growing degree days, base 45°F
4,477
Growing degree days, base 50°F
3,322
Growing degree days, base 55°F
2,329
Growing degree days, base 60°F
1,484

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January97006
February79408
March653043
April3585159
May14348377
June20155585
July2253716
August3224687
September56101496
October32010198
November629037
December87309

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 12.8 km from Chilhowie. 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 USC00447506 (Saltville 1N). Public domain.