Orange County climate

Orange County Frost Dates and Growing Season

NOAA 1991-2020 normals for Paoli, 1.7 km from Orange County, elevation 560 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Paoli. 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 21 and the first fall freeze around October 18, a growing season of about 178 days.

Median at 36°F
last May 1, first October 9
Median at 32°F
last April 21, first October 18
Median at 28°F
last April 8, first October 29

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 7May 4May 1Apr 29Apr 25Apr 21Apr 17
32°FMay 7May 2Apr 29Apr 25Apr 21Apr 18Apr 15Apr 11Apr 6
28°FApr 25Apr 19Apr 14Apr 11Apr 8Apr 5Apr 2Mar 30Mar 23
24°FApr 13Apr 6Apr 2Mar 31Mar 28Mar 24Mar 20Mar 16Mar 9
20°FMar 31Mar 27Mar 22Mar 19Mar 16Mar 12Mar 9Mar 4Feb 27
16°FMar 22Mar 17Mar 12Mar 9Mar 5Mar 1Feb 26Feb 19Feb 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°FSep 28Oct 1Oct 4Oct 7Oct 9Oct 12Oct 14Oct 17Oct 21
32°FOct 6Oct 10Oct 13Oct 16Oct 18Oct 21Oct 23Oct 25Oct 29
28°FOct 15Oct 21Oct 23Oct 26Oct 29Oct 31Nov 2Nov 5Nov 11
24°FOct 25Oct 31Nov 2Nov 4Nov 7Nov 10Nov 14Nov 18Nov 26
20°FNov 5Nov 9Nov 13Nov 17Nov 21Nov 24Nov 29Dec 2Dec 9
16°FNov 14Nov 20Nov 24Nov 28Dec 1Dec 5Dec 10Dec 16Dec 24

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°F177172167164160156152148142
32°F198191187182178174170164158
28°F221214210206201198193189181
24°F249243236231226221215211204
20°F277267260255249244239234226
16°F300291285279274268262256246

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
5,049
Cooling degree days, base 65°F
1,089
Growing degree days, base 40°F
6,106
Growing degree days, base 45°F
4,820
Growing degree days, base 50°F
3,677
Growing degree days, base 55°F
2,675
Growing degree days, base 60°F
1,812

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06007
February858010
March681255
April34916187
May12190438
June14230666
July1328792
August3285747
September67121505
October32117209
November639151
December936011

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 1.7 km from Orange 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 USC00126705 (Paoli). Public domain.