Doylestown climate

Doylestown Frost Dates and Growing Season

NOAA 1991-2020 normals for Doylestown AP, 2.3 km from Doylestown, elevation 394 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Doylestown 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 13 and the first fall freeze around October 30, a growing season of about 198 days.

Median at 36°F
last April 27, first October 18
Median at 32°F
last April 13, first October 30
Median at 28°F
last April 2, first November 10

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 11May 6May 2Apr 30Apr 27Apr 24Apr 21Apr 18Apr 14
32°FApr 27Apr 22Apr 19Apr 16Apr 13Apr 11Apr 7Apr 4Apr 1
28°FApr 14Apr 9Apr 6Apr 3Apr 2Mar 31Mar 28Mar 23Mar 17
24°FApr 3Mar 31Mar 28Mar 25Mar 21Mar 18Mar 15Mar 11Mar 6
20°FMar 27Mar 21Mar 18Mar 15Mar 12Mar 8Mar 5Feb 28Feb 22
16°FMar 19Mar 13Mar 8Mar 4Feb 28Feb 24Feb 19Feb 13Feb 5

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 5Oct 9Oct 12Oct 15Oct 18Oct 21Oct 24Oct 28Nov 1
32°FOct 15Oct 20Oct 24Oct 27Oct 30Nov 1Nov 4Nov 8Nov 12
28°FOct 27Nov 1Nov 4Nov 7Nov 10Nov 12Nov 16Nov 19Nov 25
24°FNov 8Nov 13Nov 17Nov 20Nov 24Nov 27Nov 30Dec 3Dec 10
20°FNov 17Nov 23Nov 29Dec 2Dec 5Dec 8Dec 14Dec 20Dec 26
16°FDec 1Dec 7Dec 12Dec 18Dec 22Dec 25Dec 30Jan 4Jan 13

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°F193187182177173169165160153
32°F217210206202198194189185176
28°F244236231227223220216211203
24°F269262255251247243237232226
20°F295287281275270265259253245
16°F320311306299295291285279268

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
5,160
Cooling degree days, base 65°F
959
Growing degree days, base 40°F
5,792
Growing degree days, base 45°F
4,526
Growing degree days, base 50°F
3,410
Growing degree days, base 55°F
2,447
Growing degree days, base 60°F
1,628

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,05203
February88805
March750026
April40611136
May15751363
June23182609
July1321786
August3267728
September58112505
October31814199
November605042
December90109

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 2.3 km from Doylestown. 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 USW00054786 (Doylestown AP). Public domain.