Wrightstown climate

Wrightstown Frost Dates and Growing Season

NOAA 1991-2020 normals for Philadelphia/mt Holly WFO, 17.2 km from Wrightstown, elevation 63 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Philadelphia/mt Holly WFO. 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 15 and the first fall freeze around October 29, a growing season of about 196 days.

Median at 36°F
last April 28, first October 17
Median at 32°F
last April 15, first October 29
Median at 28°F
last April 1, first November 7

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 13May 7May 3Apr 30Apr 28Apr 25Apr 22Apr 19Apr 15
32°FApr 29Apr 24Apr 20Apr 18Apr 15Apr 12Apr 9Apr 6Apr 1
28°FApr 15Apr 10Apr 6Apr 4Apr 1Mar 31Mar 27Mar 23Mar 18
24°FApr 3Mar 31Mar 27Mar 23Mar 20Mar 18Mar 14Mar 11Mar 5
20°FMar 23Mar 19Mar 16Mar 12Mar 9Mar 6Mar 3Feb 28Feb 22
16°FMar 16Mar 9Mar 5Mar 1Feb 27Feb 23Feb 19Feb 14Feb 7

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 4Oct 8Oct 11Oct 14Oct 17Oct 21Oct 24Oct 27Oct 31
32°FOct 14Oct 19Oct 23Oct 26Oct 29Nov 1Nov 2Nov 5Nov 10
28°FOct 26Oct 31Nov 2Nov 4Nov 7Nov 10Nov 13Nov 15Nov 21
24°FNov 4Nov 9Nov 13Nov 15Nov 18Nov 21Nov 25Nov 30Dec 5
20°FNov 15Nov 20Nov 25Nov 29Dec 1Dec 5Dec 9Dec 16Dec 23
16°FNov 30Dec 5Dec 10Dec 14Dec 19Dec 24Dec 28Jan 1Jan 9

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°F191185180176172168164159152
32°F214207203199196192188183176
28°F238231226222218215211207200
24°F265256252247243239234228222
20°F292283276272267262257252243
16°F318310305300295289284277269

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
5,279
Cooling degree days, base 65°F
975
Growing degree days, base 40°F
5,735
Growing degree days, base 45°F
4,485
Growing degree days, base 50°F
3,390
Growing degree days, base 55°F
2,443
Growing degree days, base 60°F
1,637

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06504
February90703
March765124
April41212131
May16452358
June22196624
July1329794
August3268730
September62107496
October34011180
November633037
December90709

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 17.2 km from Wrightstown. 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 USC00286964 (Philadelphia/mt Holly WFO). Public domain.