With a frontal boundary approaching the region, the region is prime for showers and storms in a humid airmass and such is the case early this morning as scattered showers are popping up in the pre-dawn hours across Central Pennsylvania south into Maryland. Scattered storms will be around through the region through the course of the day. It appears the the best chance of thunder will be around west and southwest of the city in the morning and afternoon, east of the city during the afternoon and evening although actual coverage may vary over the course of the day.
Any shower and storm that you get today could produce locally heavy rainfall. Severe weather does not appear likely, however, as clouds will be around a large chunk of the region.
In terms of temperatures, we should be a notch "cooler"...used loosely as a term, of course. Expect highs in the mid 80's in most spots -- generally 83-86 depending on location, although with showers and storms around some spots may end up a notch or two cooler than that depending on cloud cover and how often it storms. When it doesn't, humidity will be around and make it feel nice and muggy.