Heat — Delaware, Pennsylvania

1999-07-23 to 1999-07-31 · Delaware, Pennsylvania

Wider weather episode

A protracted run of days with consecutive high temperatures of 90 degrees or higher began on July 23rd in Southeast Pennsylvania. It lasted as long as 16 days near the Maryland border through August 7th. Dispersed within this run were two periods of both excessive heat and humidity: from July 23rd through July 25th and again from July 29th through August 1st. There were nine heat related deaths during this hot spell, four in July and five in early August. A cold front moved through the area on the 25th and brought in drier air. High temperatures still reached into the 90s from the 26th through the 28th. The humidity and higher temperatures returned on the 29th. A strong cold front moved through the region the afternoon and evening of August 1st. This brought in considerably drier air, the driest air since mid-July. Because of the extremely dry ground conditions, high temperatures kept on reaching around 90 degrees through the 7th. That day a stronger cold front brought in a cooler air mass from Canada into the northeastern United States. The string of 12 consecutive days with high temperatures of 90 degrees or higher at Philadelphia International Airport was the longest since the summer of 1995. There were nine heat related deaths during this run of oppressive weather, four occurred in July, five in August. One death occurred in Delaware County and the other three were in Philadelphia. In Delaware County a 59-year-old male was discovered dead in his house on the 24th. All the windows in the house were shut and there was no air conditioning. Similar circumstances occurred with the three heat related deaths within Philadelphia. The continued excessive heat and lack of rain parched non-irrigated farms across the state.For most places the highest temperatures during this hot spell occurred on the 28th and 31st. They included 102 degrees in Valley Forge (Chester County), 101 degrees in Hamburg (Berks County), Sellersville (Bucks County), and Easton (Northampton County), 100 degrees in Pottstown (Montgomery County), Reading (Berks County) and in the Franklin Institute within Philadelphia, 99 degrees at the Philadelphia and Lehigh Valley International Airports, Bath (Northampton County) and Morgantown (Berks County), 98 degrees at the Northeast Philadelphia Airport and Doylestown (Bucks County), 97 degrees at the Willow Grove NAS (Montgomery County) and East Stroudsburg (Monroe County) and 96 degrees in West Chester (Chester County). The Poconos offered some relief from the heat has high temperatures occasionally failed to reach 90 degrees during this 16 day period, especially in the higher terrain. New daily record high temperature records were set on the 24th at the Lehigh Valley International Airport (95 degrees) and the Philadelphia International Airport (96 degrees) on the 26th.

Source: NOAA Storm Events Database, event_id 5715611. Narrative written by the NWS forecast office that issued the report.