Chesterbrook climate

Chesterbrook Frost Dates and Growing Season

NOAA 1991-2020 normals for Phoenixville 1 E, 5.8 km from Chesterbrook, elevation 85 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Phoenixville 1 E. 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 18 and the first fall freeze around October 27, a growing season of about 192 days.

Median at 36°F
last April 30, first October 15
Median at 32°F
last April 18, first October 27
Median at 28°F
last April 3, first November 6

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 6May 2Apr 30Apr 27Apr 24Apr 21Apr 17
32°FMay 4Apr 29Apr 25Apr 21Apr 18Apr 15Apr 12Apr 7Apr 3
28°FApr 18Apr 13Apr 9Apr 6Apr 3Apr 1Mar 30Mar 25Mar 20
24°FApr 4Apr 1Mar 30Mar 26Mar 23Mar 19Mar 16Mar 13Mar 7
20°FMar 27Mar 21Mar 16Mar 14Mar 11Mar 8Mar 4Mar 1Feb 23
16°FMar 16Mar 12Mar 7Mar 3Feb 28Feb 25Feb 21Feb 15Feb 6

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 2Oct 6Oct 9Oct 12Oct 15Oct 18Oct 22Oct 26Nov 1
32°FOct 12Oct 17Oct 20Oct 24Oct 27Oct 31Nov 1Nov 4Nov 9
28°FOct 24Oct 30Nov 1Nov 3Nov 6Nov 10Nov 13Nov 17Nov 23
24°FNov 4Nov 9Nov 12Nov 16Nov 19Nov 23Nov 27Dec 1Dec 6
20°FNov 14Nov 21Nov 26Dec 1Dec 3Dec 6Dec 10Dec 15Dec 24
16°FNov 29Dec 4Dec 10Dec 14Dec 18Dec 23Dec 29Jan 2Jan 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°F189181175172168163159153146
32°F212206200195192187182176168
28°F238230225221217213209205198
24°F264256250245241236232228221
20°F291282277272267262257250243
16°F317308302297292287282275266

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
4,985
Cooling degree days, base 65°F
1,151
Growing degree days, base 40°F
6,082
Growing degree days, base 45°F
4,799
Growing degree days, base 50°F
3,668
Growing degree days, base 55°F
2,689
Growing degree days, base 60°F
1,850

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,02603
February87505
March717031
April37112154
May13574407
June15228663
July0369834
August2317780
September54134530
October30417209
November599045
December88809

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 5.8 km from Chesterbrook. 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 USC00366927 (Phoenixville 1 E). Public domain.