The Brief Thunderstorms are expected across the Philadelphia region Saturday afternoon. Summer thunderstorms are rolling through the Philadelphia area Saturday afternoon, as high temperatures and humidity push the region into a heat wave. Philadelphia heat waveWhat we know:Temperatures stayed hot Saturday, pushing into the low 90s in Philadelphia, and parts of Delaware and New Jersey. Most of the region remains under a Heat advisory through Saturday, with heat indexes as high as 102 degrees possible. The FOX 29 Weather Authority predicts thunderstorms will be possible in the afternoon on Tuesday.