Sullivan County climate

Sullivan County Frost Dates and Growing Season

NOAA 1991-2020 normals for Bristol Tri City AP, 10 km from Sullivan County, elevation 1500 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bristol Tri City 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 16 and the first fall freeze around October 24, a growing season of about 190 days.

Median at 36°F
last April 29, first October 15
Median at 32°F
last April 16, first October 24
Median at 28°F
last April 1, first November 1

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 17May 11May 6May 3Apr 29Apr 26Apr 23Apr 19Apr 14
32°FMay 5Apr 27Apr 22Apr 19Apr 16Apr 13Apr 9Apr 5Mar 30
28°FApr 18Apr 12Apr 8Apr 4Apr 1Mar 30Mar 27Mar 22Mar 16
24°FApr 5Mar 31Mar 27Mar 24Mar 21Mar 17Mar 13Mar 8Feb 28
20°FMar 26Mar 19Mar 15Mar 10Mar 5Feb 28Feb 25Feb 19Feb 10
16°FMar 18Mar 8Mar 1Feb 25Feb 18Feb 12Feb 6Jan 31Jan 22

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 4Oct 7Oct 10Oct 13Oct 15Oct 18Oct 20Oct 24Oct 28
32°FOct 11Oct 15Oct 18Oct 21Oct 24Oct 26Oct 29Nov 1Nov 4
28°FOct 19Oct 24Oct 27Oct 30Nov 1Nov 3Nov 6Nov 10Nov 15
24°FOct 30Nov 2Nov 6Nov 9Nov 12Nov 15Nov 18Nov 23Nov 29
20°FNov 9Nov 14Nov 18Nov 23Nov 27Nov 30Dec 3Dec 8Dec 17
16°FNov 22Nov 29Dec 4Dec 8Dec 12Dec 17Dec 23Dec 28Jan 5

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°F188182177172169165160155147
32°F210202198194190185181175166
28°F235227222217212209204199192
24°F263253246241237232227221213
20°F294284276270265260254247238
16°F329317308301296289282276263

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
4,150
Cooling degree days, base 65°F
1,105
Growing degree days, base 40°F
6,574
Growing degree days, base 45°F
5,156
Growing degree days, base 50°F
3,903
Growing degree days, base 55°F
2,814
Growing degree days, base 60°F
1,882

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January887012
February699019
March547179
April27313225
May9181458
June7225667
July0327792
August1295759
September36142557
October25919253
November557162
December795019

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 10 km from Sullivan County. 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 USW00013877 (Bristol Tri City AP). Public domain.