When temperatures are already pushing 80 shy of 8 AM one can easily deduce it's going to be a nasty day outside. With the combination of hot temperatures and dew point values near 70, the resulting heat index value will probably rise to near 100 degrees at the hottest times of the day. The result of that is heat advisories (orange counties) and excessive heat warnings (magenta shading) starting at 11 AM.
Our highest temperature this year so far is 93 -- we probably exceed that by day's end with a run towards 95 for many location away from the ocean. Thanks to upwelling at the ocean, which is producing water temperatures in the upper 50's and low 60's, temperatures at the Shore will be kept down by a good ten degrees...perhaps more right at the beach. That relief will not spread very far inland.
One can't rule out the risk of pop up thunder this afternoon in Pennsylvania...the "best" chances (and they're about 20-30 percent) are across Central and Northeastern Pennsylvania. I doubt we see anything around Philadelphia or points south.