The Health Department said the 67-year-old man died at his home. The cause of death was ruled to be a combination of heart disease and heat exposure.
Officials say the home had the windows closed, the air conditioning off and no fan was present.
Five people have died so far this year in Philadelphia because of the heat.
That news comes as Philadelphia broke a temperature record for a second day in a row with an official reading of 101 degrees.
Forecasters said the old record for the date was 99 degrees. The Philadelphia temperature hit 103 degrees Friday, also a record for the date.
An all-time record of 106 degrees was recorded Friday in Reading in eastern Pennsylvania, and a record 104 degrees in Allentown, while Pittsburgh tied a record with 96 degrees on Friday.
Authorities in central Pennsylvania said two men died in York County of hyperthermia during the ongoing heat wave. Both deaths were ruled accidental and due to hyperthermia.
The heat knocked out power to an eastern Pennsylvania hospital for about seven hours overnight, forcing it to run on emergency power.St. Luke's Hospital-Fountain Hill supervisor Tuesday Smith told The (Allentown) Morning Call that the hospital was not evacuated and no patients were endangered when a transformer failed. She said all systems were up and running by 4:30 a.m.
Temperatures were near or just above 100 degrees in most areas of New Jersey on Saturday afternoon, with heat indexes ranging from 105 to 110 degrees, and new same-day records were set in three of the state's major cities - Atlantic City, Newark and Trenton.