New York - New York City was under a blizzard warning on Monday ahead of a storm forecast to dump up to 60cm to 75cm of snow on the densely populated northeastern United States.
While light flurries produced about 2cm of snow in New York on Monday morning, heavy snow was forecast to start falling by the afternoon and continue into Tuesday.
"This literally could be one of the top two or three storms in the history of this city, and we need to plan accordingly," Mayor Bill de Blasio said.
"Now is the time to get ready," he said, urging residents to avoid travel later on Monday.
The storm could potentially break the city's current snowfall-record of 68.3cm measured in Central Park after a historic storm in February 2006.
Most schools were open on Monday in the city. However, they are expected to remain closed on Tuesday.
The storm, which is moving northeast, dumped about 20cm of snow on parts of Pennsylvania by Monday morning and is expected to intensify as it approaches New York City and Boston, according to the National Weather Service.
Coastal blizzard warnings extend from the state of New Jersey up the US Atlantic seaboard into Canada.
Winds of 50km/h or more are expected, with gusts potentially twice as strong, raising a threat of damage to electric lines and power outages.
Connecticut Governor Dannel Malloy declared a state of emergency on Monday and ordered a complete travel ban starting 21:00 on Tuesday.
"People need to take this storm seriously," Malloy said.
"If current predictions are accurate, we will need people to stay off the roads so that emergency personnel and utility crews can get to the places they need to get to, and to make sure that our ploughs can keep critical roadways clear."