Roan Mountain climate

Roan Mountain Frost Dates and Growing Season

NOAA 1991-2020 normals for Roan Mtn 3SW, 4.3 km from Roan Mountain, elevation 2923 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Roan Mtn 3SW. 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 12, a growing season of about 165 days.

Median at 36°F
last May 10, first October 3
Median at 32°F
last April 30, first October 12
Median at 28°F
last April 20, first October 23

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 19May 16May 13May 10May 7May 5May 1Apr 26
32°FMay 16May 11May 7May 3Apr 30Apr 28Apr 24Apr 21Apr 17
28°FMay 6Apr 30Apr 25Apr 22Apr 20Apr 17Apr 14Apr 11Apr 6
24°FApr 20Apr 16Apr 13Apr 9Apr 7Apr 4Apr 1Mar 28Mar 23
20°FApr 9Apr 4Apr 1Mar 29Mar 26Mar 21Mar 18Mar 14Mar 8
16°FMar 31Mar 25Mar 20Mar 16Mar 12Mar 9Mar 4Feb 28Feb 21

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 20Sep 24Sep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 15
32°FOct 1Oct 5Oct 7Oct 10Oct 12Oct 15Oct 17Oct 20Oct 25
28°FOct 11Oct 15Oct 17Oct 20Oct 23Oct 25Oct 28Oct 31Nov 4
24°FOct 20Oct 24Oct 26Oct 30Nov 1Nov 3Nov 5Nov 9Nov 14
20°FOct 30Nov 2Nov 5Nov 8Nov 11Nov 14Nov 17Nov 22Nov 29
16°FNov 6Nov 11Nov 15Nov 19Nov 23Nov 26Dec 1Dec 5Dec 14

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°F165159154149145142138134126
32°F184177173168165161156150143
28°F205197193189185181177172166
24°F228221216211207203199195189
20°F257247241235231227222217211
16°F285274266261255250244238231

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
5,145
Cooling degree days, base 65°F
367
Growing degree days, base 40°F
5,123
Growing degree days, base 45°F
3,814
Growing degree days, base 50°F
2,679
Growing degree days, base 55°F
1,716
Growing degree days, base 60°F
941

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January98407
February795012
March685031
April4122125
May19614302
June4870473
July8141598
August15107556
September10830375
October3563160
November662031
December877010

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 4.3 km from Roan Mountain. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00407770 (Roan Mtn 3SW). Public domain.