With an expected high of near 100 degrees, the Philadelphia region stands a good chance of hitting a record high for the date.
The record for June 21 is 99, and the forecast from the National Weather Service in Mount Holly is one degree above that. So there's a solid shot at tying or breaking the record that has stood since 1923.
And, with heat index values approaching 104 with humidity factored in, the National Weather Service has issued an excessive heat warning through 6 a.m. Friday. Indeed, there has been little relief at night, with lows in the high 70s, nearing 80, posing a real danger to those without air-conditioning.