Deadly Tropical Storm Isaias knocked out power to millions on the US east coast after making landfall in North Carolina as a hurricane.
Two people died when a tornado struck a mobile home park. At least two others in New York and Maryland also died.
The National Hurricane Center (NHC) had warned of "the danger of life-threatening storm surge".
The storm, with 65mph (100km/h) winds, moved through New York state on Tuesday afternoon, reports BBC.
It is the ninth named storm of the year.
From North Carolina up to New York, Isaias left more than 3.4 million residents without power. It has spawned tornadoes, uprooted trees, damaged homes and caused floods and fires.
Isaias was downgraded to a tropical storm after hitting islands in the Caribbean last week, but was re-categorised as a category-one hurricane as it approached the Carolinas on Monday.
It was then downgraded again to a tropical storm, but storm surge warnings remain in effect along the coast.
As of Tuesday evening, Isaias was moving north at 40mph (65km/h), the NHC said. It is expected to follow a northward path through the evening, reaching southern Canada by late Tuesday.
Strong winds, with gusts reaching hurricane force, are expected all along the Mid-Atlantic coast and as far as New England on Tuesday.
As of Tuesday afternoon, local time, the storm was sprinting across eastern New York towards southern New England with strong and damaging winds. By early evening, tornado watch for eastern New York had been cancelled. As the storm receded, the Staten Island Ferry resumed limited service, New York City Mayor Bill de Blasio said, with hourly service to resume overnight.
Parts of New York state, through the Hudson River Valley, were expected to experience flash flooding after hours of heavy rain.
A tropical storm warning remained in effect up the north-east coast all the way to Maine, with major cities like Washington, Philadelphia and New York in the potential path. By Tuesday morning, the Mid-Atlantic coast was experiencing heavy rains with warnings of flash floods spanning from Maryland to Pennsylvania.
Police in New York City said a tree fell and killed a man inside his vehicle in Queens. A woman in Maryland was also killed when a tree toppled on to her car in the storm.
Tornadoes were still possible from New York to New England in the evening, the NHC said.