Ritchie County climate

Ritchie County Frost Dates and Growing Season

NOAA 1991-2020 normals for Harrisville, 4.7 km from Ritchie County, elevation 823 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Harrisville. 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 26 and the first fall freeze around October 17, a growing season of about 173 days.

Median at 36°F
last May 5, first October 7
Median at 32°F
last April 26, first October 17
Median at 28°F
last April 15, first October 27

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 17May 12May 9May 5May 2Apr 30Apr 26Apr 22
32°FMay 14May 8May 3Apr 30Apr 26Apr 24Apr 20Apr 18Apr 14
28°FApr 30Apr 23Apr 20Apr 18Apr 15Apr 12Apr 9Apr 6Apr 1
24°FApr 16Apr 11Apr 7Apr 4Apr 2Mar 31Mar 27Mar 24Mar 18
20°FApr 4Mar 31Mar 28Mar 24Mar 20Mar 17Mar 13Mar 9Mar 1
16°FMar 27Mar 20Mar 16Mar 13Mar 9Mar 4Mar 1Feb 26Feb 18

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 27Oct 1Oct 3Oct 5Oct 7Oct 10Oct 12Oct 15Oct 20
32°FOct 5Oct 9Oct 12Oct 14Oct 17Oct 20Oct 22Oct 25Oct 29
28°FOct 13Oct 18Oct 21Oct 24Oct 27Oct 29Nov 1Nov 4Nov 9
24°FOct 24Oct 29Nov 1Nov 3Nov 6Nov 9Nov 11Nov 15Nov 20
20°FNov 2Nov 7Nov 11Nov 14Nov 18Nov 21Nov 25Nov 30Dec 5
16°FNov 12Nov 20Nov 24Nov 29Dec 1Dec 6Dec 10Dec 18Dec 25

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°F173167162158154150145140133
32°F191185180177173169165159152
28°F213207202198195192188182176
24°F239231227222218213210205199
20°F270260253247243238233227221
16°F298288280275269264259253243

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
5,236
Cooling degree days, base 65°F
845
Growing degree days, base 40°F
5,702
Growing degree days, base 45°F
4,439
Growing degree days, base 50°F
3,327
Growing degree days, base 55°F
2,356
Growing degree days, base 60°F
1,526

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06907
February881013
March719144
April3817159
May14465394
June19164596
July3263725
August4234694
September7898472
October35812180
November657036
December92508

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 4.7 km from Ritchie 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 USC00463940 (Harrisville). Public domain.