Morrell Park climate

Morrell Park Frost Dates and Growing Season

NOAA 1991-2020 normals for Philadelphia Ne AP, 2.2 km from Morrell Park, elevation 100 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Philadelphia Ne 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 4 and the first fall freeze around November 7, a growing season of about 216 days.

Median at 36°F
last April 17, first October 27
Median at 32°F
last April 4, first November 7
Median at 28°F
last March 23, first November 19

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 3Apr 28Apr 23Apr 20Apr 17Apr 14Apr 11Apr 7Apr 3
32°FApr 17Apr 13Apr 9Apr 6Apr 4Apr 1Mar 31Mar 27Mar 21
28°FApr 5Apr 1Mar 30Mar 26Mar 23Mar 20Mar 17Mar 14Mar 8
24°FMar 26Mar 21Mar 17Mar 14Mar 12Mar 9Mar 5Mar 1Feb 24
20°FMar 18Mar 12Mar 7Mar 4Mar 1Feb 25Feb 21Feb 16Feb 9
16°FMar 6Mar 1Feb 25Feb 19Feb 14Feb 10Feb 5Jan 31Jan 21

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 12Oct 17Oct 21Oct 24Oct 27Oct 30Nov 1Nov 5Nov 9
32°FOct 24Oct 29Nov 1Nov 4Nov 7Nov 10Nov 13Nov 16Nov 22
28°FNov 4Nov 9Nov 12Nov 15Nov 19Nov 22Nov 26Dec 1Dec 5
24°FNov 14Nov 21Nov 25Nov 29Dec 2Dec 5Dec 9Dec 15Dec 23
20°FNov 28Dec 4Dec 8Dec 13Dec 18Dec 23Dec 28Jan 1Jan 7
16°FDec 10Dec 19Dec 26Jan 1Jan 3Jan 7Jan 12Jan 18Jan 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°F212205200196193188184179173
32°F236229224220216212208203197
28°F264255249246241236232226220
24°F289280275269264260255249243
20°F316307301295291286281274266
16°F341332326321316311305299290

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
97% 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
4,466
Cooling degree days, base 65°F
1,375
Growing degree days, base 40°F
6,625
Growing degree days, base 45°F
5,263
Growing degree days, base 50°F
4,064
Growing degree days, base 55°F
3,020
Growing degree days, base 60°F
2,126

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January95506
February79809
March655144
April32819186
May10684444
June10268708
July0428893
August1369834
September32176594
October24828264
November526166
December808017

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 2.2 km from Morrell Park. 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 USW00094732 (Philadelphia Ne AP). Public domain.