The Flash Flood Warning, for Westchester, Rockland and Orange counties, is in effect until 9:45 p.m. Tuesday.
The Flood Advisory, for Putnam and Fairfield counties, is in effect until 9:15 p.m.
Just before 7 p.m., Doppler radar indicated thunderstorms producing heavy rain across the area.
Flash flooding is expected to begin shortly.
Some locations that will experience flooding include New City, Newburgh, Middletown, Ossining, Peekskill, Monsey, Nanuet, Haverstraw, Tarrytown, Mount Kisco, Suffern, Port Jervis, Monroe and Walden, the National Weather Service said.
A Tornado Watch remains in effect until midnight.
A severe storm that moved through from west to east late in afternoon has caused downed trees leading to road closures and Metro-North service interruptions on the Harlem Line as well as thousands of power outages, mainly in Northern Westchester and Fairfield County.
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