The large weather system spanned from Baltimore to Boston Wednesday, dropping at least 2 inches of rain on 58 million people. Isolated areas saw up to 10 inches of rain.
The intensity of the storm caught officials and commuters off guard. The Philadelphia and New York City corridor experienced rain rates of 2 to 3 inches per hour. Newark, N.J., recorded 3.24 inches of its 8.44 inch total between 8 p.m. and 9 p.m. In Central Park, 3.15 inches fell in an hour, the highest amount on record.
When declaring flash-flood guidance, the National Weather Service said that less rainfall is required to produce flash flooding in urban areas.