Small-stream flooding started across the region after the heavy rain on Sunday.
A state of emergency was declared in that Salem County township and also in Cumberland County, officials said.
Flights were delayed at Philadelphia International Airport, at Newark Liberty Airport, LaGuardia and Kennedy airports in New York.
The National Weather Service reported: “The heaviest rain has been in northeastern Maryland, northern Delaware, and southwestern New Jersey”.
Police said, in Philadelphia water was covering portions of Lincoln Drive.
Around noon, the weather service issued a tornado warning for central Delaware.