Five states declared an emergency hours before heavy snow and hurricane-force winds blasted the area.
Experts warn of "historic" snowfall in some places, and flood warnings have been issued near the coast. More than 5000 US flights have been cancelled.
As the storm arrived, more than 116,000 households across Massachusetts were without power.
Forecasters said there was a chance the storm, known as a Nor'easter, will blanket the Boston area with up to 61cm of snow, and up to 30cm of snow has already fallen in parts of New York.
