Blizzard warnings were in effect for the northeastern coast, including the New York metropolitan area, the National Weather Service said.
"Travel conditions will continue to be extremely hazardous if not impossible," it said.
The storm was expected to taper off from west to east into the afternoon. Snowfall is forecast to total from 2 to 3 feet (60 to 75 cm) in eastern Massachusetts, Rhode Island and Connecticut, the weather service said in a statement.
In the first death blamed on the blizzard, a man in his 70s was killed when a driver lost control of her car and hit him in Poughkeepsie, New York, media reported.
Utility companies reported about 600,000 customers without power across Massachusetts, Rhode Island and Connecticut as the wet, heavy snow brought down trees and lines.
Rhode Island Governor Lincoln Chafee said 180,000 state residents had been left in the dark. National Guard troops were rescuing stranded motorists, especially on unplowed on-ramps, he said.
"We need people to stay off the roads right now. That's critical," he told CNN.
The Pilgrim Nuclear Power Plant in Plymouth, Massachusetts, lost power and automatically shut down late on Friday, but there was no threat to the public, the Nuclear Regulatory Commission said.
Hartford, Connecticut, was blanketed by 34 inches (85 cm) of snow and St. James, New York, recorded 27.5 inches (69 cm), with more coming down, the weather service said.
Hartford Mayor Pedro Segarra said street-clearing crews had been forced to suspend operations as snow fell at a rate of more than 4 inches (10 cm) an hour.
"I've never seen snow fall like this all at once," he told CNN.
The heavy snowfall was backed by winds that gusted to 83 miles an hour (133 km an hour) at Cuttyhunk, New York, and brought down trees across the region, the weather service said.
The storm also posed a risk of flooding at high tide to areas still recovering from October's Superstorm Sandy.
The governors of Massachusetts, Rhode Island, Connecticut, New York and Maine declared states of emergency before the storm. Thousands of flights were canceled.
Massachusetts Governor Deval Patrick banned most car travel starting Friday afternoon. Connecticut Governor Dannel Malloy closed the state's highways to all but emergency vehicles.
The town of Wakefield, Massachusetts, north of Boston, told residents in an electronic phone message to stay off roads until 7 a.m. on Sunday.
Amtrak suspended railroad service between New York, Boston and points north on Friday afternoon.
The town of Gorham, Maine, was buried under more than 31 inches (78 cm) of snow, and Philip Gagnon, chairman of the town council, said many roads would not be cleared until late Sunday or Monday.
"We've had our crews out since yesterday morning," he said. "It's going to probably take some time because they can only do so much before we can rest them," he said.
In New York, Mayor Michael Bloomberg suggested people relax at home - cook or watch a movie. Bloomberg said he planned to catch up on his sleep.