It said the latest victim was a 22-year-old Brooklyn man. He died Sunday when temperatures hit 93 in Central Park.
Two other people died of heat exposure on July 6 when temperatures soared to 103. They were a 46-year-old woman and a 70-year-old man, both from Queens.
The medical examiner said all three individuals died of hyperthermia or exposure to excessive environmental temperature.
The National Weather Service says that to date the average temperature this July has been 81.8.
The warmest July on record was in 1999 when the average temperature was 81.4.