The National Weather Service in Mount Holly, New Jersey, issued a severe thunderstorm warning Tuesday night for parts of Philadelphia, Montgomery and Bucks counties as dangerous heat and humidity continued across the region. The warning was in effect until 8:45 p.m. Tuesday, May 19, while a heat advisory remained in place through 8:00 p.m. Wednesday.
At 8:04 p.m., radar detected a severe thunderstorm over Feasterville, about 13 miles west of Trenton, moving east at 20 mph. Forecasters said the storm could bring wind gusts up to 60 mph and penny-size hail, and they told residents in Philadelphia, Trenton, Bensalem, Bristol and nearby communities to move to an interior room on the lowest floor of a building for protection.
The weather was already punishing before the storm arrived. The heat index was expected to reach 99 degrees, with the highest values during the afternoon and again on Wednesday. The National Weather Service warned that hot temperatures and high humidity could cause heat illnesses, and it urged people to drink plenty of fluids, stay in air-conditioned rooms, avoid the sun and check on relatives and neighbors.
Tuesday’s high of 98 degrees set a new record for Philadelphia’s hottest May day on record, a sign of how early the season’s heat has arrived. The heat advisory covered New Castle County in Delaware, several counties in New Jersey including Mercer and Camden, and parts of southeastern Pennsylvania including Philadelphia, Delaware and Montgomery counties.
That overlap of record heat and fast-moving storms made Tuesday night the most difficult stretch of the day for people across the region. The storm threat was expected to ease after 8:45 p.m., but the heat advisory kept the larger warning in place into Wednesday evening, leaving the area under a second round of stress from the same early-season heat wave.
