30-year climate normals

Chester County Climate and Weather Averages

Hottest month — July

83.6°

average daily high. The coldest month is January, averaging a low of 22.7°F.

Chester County gets 47.14" of precipitation a year, and 27% of it falls in Jul, Aug, Sep.

Temperature through the year

Each bar spans the average daily low to the average daily high for that month.

Month	Avg high	Avg low	Precip
January	38.6°	22.7°	3.62"
February	41.2°	24.0°	3.12"
March	49.8°	31.0°	4.40"
April	61.5°	40.2°	3.79"
May	71.2°	50.2°	3.58"
June	79.5°	59.0°	4.43"
July	83.6°	63.7°	4.17"
August	81.5°	61.9°	4.28"
September	75.3°	55.2°	4.47"
October	63.9°	43.8°	4.03"
November	53.3°	34.3°	3.22"
December	43.2°	27.6°	4.03"

Rainfall by month

Precipitation is spread fairly evenly through the year here, with 27% falling in the wettest three months (Jul, Aug, Sep).

January 3.62"

February 3.12"

March 4.40"

April 3.79"

May 3.58"

June 4.43"

July 4.17"

August 4.28"

September 4.47"

October 4.03"

November 3.22"

December 4.03"

Annual total 47.14"

What this climate costs you

Degree days measure how hard a building has to work to stay comfortable. They are the reason two identical houses have very different power bills, and they are the link between the weather here and what you pay every month.

Cooling degree days How much air conditioning the climate demands 778

Heating degree days How much heating the climate demands 5,359

Approximate annual cooling cost At 21.55¢/kWh, Pennsylvania average $168

Approximate annual electric heating cost Lower where heating is gas rather than electric $404

These are rough planning figures from degree days and the state electricity price, not a bill estimate. House size, insulation and fuel type move them a lot. See the full cost of owning a home in Chester County, where electricity is one line of eight.

Common questions

What is the weather like in Chester County?

Chester County averages a high of 83.6°F in July and a low of 22.7°F in January. Annual precipitation is 47.14 inches, with essentially no snow.

When is the rainy season in Chester County?

The wettest stretch is Jul, Aug, Sep, which accounts for 27% of the year's precipitation. Precipitation is relatively evenly distributed across the year.

How hot does it get in Chester County?

The average daily high in July, the hottest month, is 83.6°F. That drives 778 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in Chester County?

Effectively no. Measurable snowfall is rare in Chester County.

Sources

Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station AVONDALE 2 N, PA US (USW00003761), 8.2 miles from the county centroid.
Heating and cooling degree days — NOAA, same station and period.
Electricity price — US Energy Information Administration, Electric Power Monthly Table 5.6.A, Pennsylvania residential average.
Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.