Glenvar climate

Glenvar Frost Dates and Growing Season

NOAA 1991-2020 normals for Roanoke Rgnl AP, 14.9 km from Glenvar, elevation 1175 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Roanoke Rgnl AP. 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 3 and the first fall freeze around November 1, a growing season of about 210 days.

Median at 36°F
last April 17, first October 22
Median at 32°F
last April 3, first November 1
Median at 28°F
last March 22, first November 12

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 7May 1Apr 25Apr 21Apr 17Apr 14Apr 11Apr 7Apr 3
32°FApr 18Apr 13Apr 9Apr 6Apr 3Apr 1Mar 29Mar 25Mar 19
28°FApr 7Apr 1Mar 29Mar 25Mar 22Mar 18Mar 15Mar 10Mar 4
24°FMar 27Mar 21Mar 17Mar 13Mar 9Mar 5Mar 1Feb 25Feb 17
20°FMar 17Mar 10Mar 5Mar 1Feb 26Feb 19Feb 13Feb 7Feb 1
16°FMar 8Mar 1Feb 24Feb 15Feb 9Feb 4Jan 31Jan 23Jan 12

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°FOct 9Oct 13Oct 16Oct 19Oct 22Oct 25Oct 28Oct 31Nov 4
32°FOct 18Oct 24Oct 27Oct 30Nov 1Nov 4Nov 6Nov 10Nov 15
28°FOct 30Nov 2Nov 5Nov 9Nov 12Nov 15Nov 19Nov 25Dec 1
24°FNov 9Nov 14Nov 18Nov 23Nov 28Dec 1Dec 5Dec 10Dec 19
20°FNov 23Dec 1Dec 4Dec 9Dec 13Dec 19Dec 24Dec 30Jan 7
16°FDec 9Dec 14Dec 21Dec 27Jan 1Jan 5Jan 11Jan 17Jan 27

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°F207200195190185181177172164
32°F231224219215210206202197189
28°F261251244239234231226221213
24°F291280273269263258253245236
20°F324313305299293287281274265
16°F353339332327320313306300291

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
95% 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
3,869
Cooling degree days, base 65°F
1,368
Growing degree days, base 40°F
7,021
Growing degree days, base 45°F
5,568
Growing degree days, base 50°F
4,276
Growing degree days, base 55°F
3,149
Growing degree days, base 60°F
2,178

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January840015
February678023
March523598
April24131265
May79113500
June8272714
July0395860
August1349814
September33169587
October21830294
November502285
December747023

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 14.9 km from Glenvar. 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 USW00013741 (Roanoke Rgnl AP). Public domain.