Harrisville climate

Harrisville Frost Dates and Growing Season

NOAA 1991-2020 normals for Slippery Rock 1 Ssw, 9.9 km from Harrisville, elevation 1260 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Slippery Rock 1 Ssw. 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 14, a growing season of about 158 days.

Median at 36°F
last May 20, first October 1
Median at 32°F
last May 7, first October 14
Median at 28°F
last April 26, 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°FJun 2May 29May 26May 22May 20May 17May 13May 8May 1
32°FMay 25May 19May 15May 11May 7May 3Apr 30Apr 27Apr 22
28°FMay 15May 9May 3Apr 29Apr 26Apr 23Apr 20Apr 16Apr 11
24°FMay 4Apr 25Apr 20Apr 17Apr 13Apr 10Apr 7Apr 3Mar 31
20°FApr 15Apr 10Apr 6Apr 3Apr 1Mar 30Mar 27Mar 21Mar 15
16°FApr 4Mar 31Mar 28Mar 24Mar 20Mar 17Mar 14Mar 11Mar 6

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 17Sep 22Sep 26Sep 29Oct 1Oct 4Oct 6Oct 9Oct 15
32°FOct 1Oct 4Oct 7Oct 10Oct 14Oct 16Oct 20Oct 24Oct 30
28°FOct 10Oct 17Oct 20Oct 24Oct 27Oct 31Nov 1Nov 5Nov 10
24°FOct 26Nov 1Nov 2Nov 5Nov 8Nov 11Nov 14Nov 17Nov 22
20°FNov 4Nov 7Nov 11Nov 14Nov 18Nov 21Nov 26Dec 1Dec 5
16°FNov 11Nov 18Nov 22Nov 26Dec 1Dec 3Dec 6Dec 11Dec 19

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°F157149144139135131126121112
32°F180173168163158153149143136
28°F202195190186183179174168160
24°F228221216211207203198194186
20°F256246241236232229224219212
16°F279270264258253248243238231

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
6,575
Cooling degree days, base 65°F
454
Growing degree days, base 40°F
4,559
Growing degree days, base 45°F
3,442
Growing degree days, base 50°F
2,473
Growing degree days, base 55°F
1,646
Growing degree days, base 60°F
964

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,23702
February1,05402
March915017
April553273
May27227253
June7885459
July17161609
August29128564
September14345358
October4565115
November758019
December1,06503

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 9.9 km from Harrisville. 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 USC00368184 (Slippery Rock 1 Ssw). Public domain.