Trexlertown climate

Trexlertown Frost Dates and Growing Season

NOAA 1991-2020 normals for Rodale Rsch Ctr, 9.8 km from Trexlertown, elevation 550 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rodale Rsch Ctr. 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 14, a growing season of about 171 days.

Median at 36°F
last May 8, first October 5
Median at 32°F
last April 26, first October 14
Median at 28°F
last April 10, first October 26

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 24May 18May 14May 10May 8May 4Apr 30Apr 26Apr 22
32°FMay 13May 7May 3Apr 30Apr 26Apr 23Apr 20Apr 16Apr 10
28°FApr 29Apr 23Apr 18Apr 14Apr 10Apr 8Apr 4Apr 2Mar 29
24°FApr 12Apr 6Apr 3Apr 1Mar 30Mar 27Mar 24Mar 19Mar 12
20°FApr 1Mar 30Mar 26Mar 23Mar 19Mar 15Mar 12Mar 7Mar 2
16°FMar 25Mar 19Mar 15Mar 12Mar 9Mar 5Mar 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 24Sep 28Oct 1Oct 3Oct 5Oct 7Oct 10Oct 13Oct 18
32°FOct 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 25Oct 31
28°FOct 10Oct 14Oct 18Oct 22Oct 26Oct 30Nov 2Nov 6Nov 12
24°FOct 20Oct 27Nov 1Nov 4Nov 8Nov 12Nov 16Nov 20Nov 27
20°FNov 4Nov 10Nov 15Nov 19Nov 22Nov 26Dec 1Dec 5Dec 10
16°FNov 18Nov 24Nov 28Dec 2Dec 6Dec 9Dec 14Dec 19Dec 30

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°F170163159155151147143137129
32°F194186180176171167162158150
28°F220213207202198193189184176
24°F246237231227222218214208201
20°F270262256252246241237232225
16°F296288281276271266262256248

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
5,674
Cooling degree days, base 65°F
779
Growing degree days, base 40°F
5,322
Growing degree days, base 45°F
4,117
Growing degree days, base 50°F
3,067
Growing degree days, base 55°F
2,156
Growing degree days, base 60°F
1,394

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12402
February96001
March809020
April4466108
May19442321
June37155568
July2270733
August7216674
September8583450
October3757154
November665030
December97205

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 9.8 km from Trexlertown. 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 USC00367578 (Rodale Rsch Ctr). Public domain.