The only certainty is the heat: mid 90s today and Wednesday, upper 90s Thursday to Saturday, low 90s Sunday. Monday might finally see a high in 80s again, after 11 days of 90 or hotter.
As for the rain, lightning and possible strong gusts, "it looks like two chances," Iovino said.
First, a system over Michigan and Wisconsin this morning seems "fairly likely" to bring a line of storms through the Philadelphia area late tonight or Wednesday morning, he said.
Then a front could spawn more scattered thunderstorms Wednesday afternoon.
If they materialize, some towns could see a period of heavy rain while neighboring places just stay hot and muggy.
The good news is that no prolonged steady showers are in the forecast.
So far, the summer has had a somewhat typical amount of rain, but hasn't erased a deficit left over from winter and spring, Iovino said.
For more on the forecast, go to http://go.philly.com/weather.
Contact staff writer Peter Mucha at 215-854-4342 or email@example.com.