The National Weather Service issued a flash flood warning for Queens, Brooklyn and Staten Island just before 12 p.m. on Wednesday.
The warning estimated that between one and two inches of rain had already fallen in Forest Hills and Jamaica, with the possibilty of another inch or two for the rest of the afternoon.
In addition to a hazardous weather outlook and a forecast for possible thunderstorms, winds of between 10 and 13 miles per hour are expected.
The NWS also warned residents not to drive on flooded roadways, as most flooding casualties occur in cars.
The flash flood warning was scheduled to stay in effect until 2 p.m. Wednesday.