The most oppressive hot spell of the summer season affected Eastern Pennsylvania from July 15th through the 20th.  Widespread high temperatures reached into the mid to upper 90s and the most oppressive days (combination of heat and humidity) occurred on the 18th and 19th. Morning lows those days were only around 80 degrees in highly urbanized areas. Afternoon heat indices reached 105 to 109 degrees in southeastern Pennsylvania and Berks County and 100 to 105 degrees elsewhere. The highest hourly heat index in Philadelphia was 107 degrees. There were two heat related deaths, both in Philadelphia. A 57-year-old male and a female died. While the 57-year-old male had an air conditioner in his home, it was not on when he was found. Four roof workers suffered heat exhaustion while working on the roof of the Chichester Middle School in Delaware County, three had to be hospitalized.

To combat the heat, many counties, cities and municipalities opened cooling centers. The hours of air-conditioned senior citizen centers were extended. In Philadelphia, the Corporation for Aging had councilors and nurses on the phone. Montgomery County issued a code red. Delaware County also provided fans to senior citizens.
Highest temperatures included 98 degrees at the Philadelphia and Lehigh Valley International Airports, 96 degrees in Reading (Berks County), West Chester (Chester County) and Fork Township (Northampton County), 95 degrees in Doylestown and Quakertown in Bucks County and 94 degrees in Pottstown (Montgomery County).
A stalling front brought an end to the excessive heat on the 21st and to 90 degree high temperatures by the 22nd.

Excessive Heat in EASTERN CHESTER, PENNSYLVANIA
From 15-JUL-13 10:00:00 to 20-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in WESTERN MONTGOMERY, PENNSYLVANIA
From 18-JUL-13 09:00:00 to 19-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in NORTHAMPTON, PENNSYLVANIA
From 19-JUL-13 09:00:00 to 19-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in LOWER BUCKS, PENNSYLVANIA
From 15-JUL-13 10:00:00 to 20-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in EASTERN MONTGOMERY, PENNSYLVANIA
From 15-JUL-13 10:00:00 to 20-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Excessive Heat in WESTERN CHESTER, PENNSYLVANIA
From 18-JUL-13 09:00:00 to 19-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Excessive Heat in LEHIGH, PENNSYLVANIA
From 19-JUL-13 09:00:00 to 19-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in DELAWARE, PENNSYLVANIA
From 15-JUL-13 10:00:00 to 20-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in LEHIGH, PENNSYLVANIA
From 18-JUL-13 09:00:00 to 18-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat in LEHIGH, PENNSYLVANIA
From 18-JUL-13 09:00:00 to 18-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat in NORTHAMPTON, PENNSYLVANIA
From 18-JUL-13 09:00:00 to 18-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in PHILADELPHIA, PENNSYLVANIA
From 15-JUL-13 10:00:00 to 20-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat in BERKS, PENNSYLVANIA
From 15-JUL-13 09:00:00 to 15-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat in LEHIGH, PENNSYLVANIA
From 15-JUL-13 09:00:00 to 15-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat in NORTHAMPTON, PENNSYLVANIA
From 15-JUL-13 09:00:00 to 15-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat in UPPER BUCKS, PENNSYLVANIA
From 15-JUL-13 09:00:00 to 15-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat in WESTERN MONTGOMERY, PENNSYLVANIA
From 15-JUL-13 09:00:00 to 15-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat in WESTERN CHESTER, PENNSYLVANIA
From 15-JUL-13 09:00:00 to 15-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Excessive Heat in BERKS, PENNSYLVANIA
From 18-JUL-13 09:00:00 to 19-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in UPPER BUCKS, PENNSYLVANIA
From 18-JUL-13 09:00:00 to 19-JUL-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS