Preston County climate

Preston County Frost Dates and Growing Season

NOAA 1991-2020 normals for Terra Alta #1, 10.7 km from Preston County, elevation 2630 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Terra Alta #1. 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 May 7 and the first fall freeze around October 11, a growing season of about 156 days.

Median at 36°F
last May 19, first October 1
Median at 32°F
last May 7, first October 11
Median at 28°F
last April 26, 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°FJun 2May 29May 25May 22May 19May 15May 11May 7May 1
32°FMay 24May 19May 15May 10May 7May 3Apr 30Apr 26Apr 21
28°FMay 15May 9May 3Apr 30Apr 26Apr 22Apr 19Apr 16Apr 10
24°FMay 1Apr 23Apr 19Apr 16Apr 13Apr 10Apr 6Apr 3Mar 30
20°FApr 16Apr 12Apr 8Apr 5Apr 3Apr 1Mar 29Mar 25Mar 19
16°FApr 9Apr 4Mar 31Mar 29Mar 25Mar 22Mar 18Mar 14Mar 8

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 19Sep 23Sep 26Sep 29Oct 1Oct 3Oct 6Oct 9Oct 13
32°FSep 27Oct 2Oct 5Oct 8Oct 11Oct 13Oct 16Oct 20Oct 23
28°FOct 8Oct 13Oct 17Oct 20Oct 23Oct 25Oct 27Oct 30Nov 3
24°FOct 20Oct 24Oct 28Oct 31Nov 1Nov 4Nov 6Nov 10Nov 16
20°FOct 31Nov 3Nov 6Nov 9Nov 11Nov 14Nov 18Nov 23Nov 29
16°FNov 6Nov 11Nov 15Nov 19Nov 23Nov 27Dec 1Dec 5Dec 11

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°F155148143138134131126122115
32°F178171166161156152147141134
28°F199192188183179175170164155
24°F223217212207203199194189180
20°F246237232228224219216212205
16°F267259253248243238233227220

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
6,562
Cooling degree days, base 65°F
276
Growing degree days, base 40°F
4,404
Growing degree days, base 45°F
3,262
Growing degree days, base 50°F
2,270
Growing degree days, base 55°F
1,427
Growing degree days, base 60°F
749

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21403
February1,02204
March893024
April522396
May28313230
June9249408
July28103539
August4180504
September16327322
October4722110
November767025
December1,06605

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 10.7 km from Preston 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 USC00468777 (Terra Alta #1). Public domain.