Governors across New England have declared states of emergencyHeavy snow is falling in the US north-east, where a "potentially historic" winter storm could bring up to 3ft (91cm) of snow in some areas. Flights to and from New York have been cancelled and power cuts are reported as blizzards from the Great Lakes descend on parts of New England.
People have been warned to stay off the roads, and stock up on food and other supplies.
Winds of up to 75mph (120km/h) were expected to create deep drifts.
The National Weather Service said the combination of two weather systems from the polar and sub-tropical jet streams would produce a "potentially historic" storm.
'State of emergency'
Blizzard warnings are in effect for parts of New Jersey, New York, Massachusetts, Rhode Island and Connecticut, and extend into New Hampshire and Maine.
The heaviest snowfall was expected overnight on Friday and in the early hours of Saturday.
By Friday afternoon governors in the states of New York, Massachusetts, New Hampshire, Rhode Island, Connecticut and Maine had declared states of emergency and driving bans.
In Rhode Island, utility companies said 45,000 people were without power with more than 8in of snow on the ground.
In Canada, meanwhile, up to 25cm of snow as well as strong wind gusts are expected in the southern part of Ontario province, with flurries also forecast in Quebec.
Ontario has already seen 200 vehicle accidents, the CBC reported. At least three people have been killed.
Snow was also blamed for a 19-car pile-up in Maine on Friday.
In Boston, where schools were preemptively closed on Friday, Mayor Thomas Menino urged businesses to consider allowing staff to stay home to reduce the risk of commuters getting stranded.
While schools and transportation in the city remain open for now, Mr Bloomberg advised New Yorkers to stock up on supplies, including medicine.
Meanwhile, meteorologists stressed the forecasts were not exaggerating the severity of the storm.
"This one doesn't come along every day. This is going to be a dangerous winter storm," said Alan Dunham, meteorologist for the National Weather Service.
"Wherever you need to get to, get there by Friday afternoon and don't plan on leaving."