US media counted up to 21 people dead as a result of the storm, which was blasting New England and eastern Canada with heavy snow and powerful winds, a day after plowing through southern and eastern US states.
One of the casualties was a 36-year-old pregnant woman, struck and killed by a snowplow in a New York parking lot. Her baby was delivered alive by Caesarean section but remains in critical condition.
Further south, the sun had come out, but roads were dangerously icy as commuters returned to their morning commute, after wet roads froze overnight.
A series of massive accidents blocked traffic on a major highway, the Pennsylvania Turnpike. Footage from traffic helicopters showed dozens of cars and trucks stuck in the pile-ups.
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A state police trooper told the Philadelphia Inquirer newspaper injuries had been reported, without giving further details.
There was to be only a temporary respite for some, with forecasters predicting yet more snow and wintry weather for the US east coast tomorrow.
But a decision to keep schools open in the country's largest city, New York, has drawn fierce criticism for new Mayor Bill De Blasio.
There were reports of school buses colliding with cars -- though no injuries -- and less than half of New York's 1.1 million students turned up.