From the National Weather Service:
Fine summer day today with temperatures by 4 PM reaching the upper 70s and 80s. Change of pace Tuesday, as an approaching cold front brings showers and scattered thunderstorms.
Lots of humidity will be in place for the storms to feed upon, so expect some local downpours. Areas that drain poorly may experience local flooding for a brief time from such downpours.
Best chance of 1-2 inches of rain will be in parts of Connecticut, Rhode Island, and Southeast Massachusetts.