The latest winter storm to hit America's East Coast grounded more than 6,500 flights as hundreds of thousands in the ice-encrusted South remained without power.
At least 21 deaths, most of them in traffic accidents, were blamed on the storm as it made its way across the South and up the coast.
Among the victims was a pregnant woman who was struck and killed by a snowplough in New York City. Her baby was delivered in a critical condition via Caesarean section.
Washington DC had at least 8ins of snow and government offices and the city's two main airports were closed. New York City had at least the same amount.
In New York, the teachers union criticised Mayor Bill de Blasio's decision to keep the schools open, but the mayor said many parents depended on schools to watch over their children while they were at work.
About 1.2 million homes and businesses lost power as the storm moved from the South through the North East. By early today, about 550,000 customers remained in the dark, mostly in South Carolina and Georgia.
Temperatures were expected to drop below freezing again today.
The recent series of storms and cold blasts - blamed in part on a kink in the jet stream, the high-altitude air currents that dictate weather - has hit retail sales across the US, the Commerce Department said. Sales dipped 0.4% in January.
"It's been a tough winter. It seems like it will never end," said Deb Ragan, clearing a pavement in Philadelphia.
The dangerous weather threatened to disrupt deliveries of Valentine's Day flowers.