Flash flood and severe thunderstorm watches are in place ahead of strong storms expected to move through the Philadelphia region Monday.
The National Weather Service says to expect periods of showers and thunderstorms throughout the day, particularly in the afternoon and evening.
The FAA was delaying flights to Philadelphia International Airport because of the storms approaching the city.
Some of the storms could bring heavy rain and strong winds. The day is otherwise expected to be warm and muggy, with high temperatures in the high 80s.
The flash flood watch is in place from noon until midnight for the region. The thunderstorm watch is in effect until 8 p.m.
Forecasters are calling for most places to see an inch or two of rain, with the potential for some areas to get three to five inches.
"The bulk of these rainfall amounts could fall in a very short period," the weather service says.
Creeks, streams and roadways, especially in urban and poor-drainage areas, are at particular risk of flooding.