Winter storm warnings were in effect Wednesday from the southern Appalachian mountains to coastal Massachusetts and were expected to expire Thursday morning, said CNN meteorologist Sean Morris.
Snow was falling about an inch an hour in Washington, D.C., which was expected to receive 4 to 6 inches Wednesday evening, he said.
Federal employees and most schools in Washington ended business early on Wednesday.
New York is expected to receive 8 to 12 inches of snow starting about midnight, Morris said.
Boston should also see 8 to 12 inches, with the heaviest snow falling Thursday morning, he said. Nashville and central Tennessee got 2 to 4 inches of snow Wednesday, Morris said.
The snowfall was even prompting airlines to pre-emptively cancel flights. Among the biggest cancellations were Delta Airlines' 575 flights between Washington, D.C., and Boston, said spokesman Anthony Black.
American Airlines/American Eagle spokesman Ed Martelle said the two airlines cancelled 280 flights for Wednesday and 65 more are cancelled for Thursday between Washington, D.C., and Boston.
United cancelled 276 flights Wednesday and proactively cancelled 71 more for Thursday, and Continental cancelled 322 flights Wednesday and 108 more for Thursday, said Christen David, spokesman for both airlines.
Southwest Airlines canceled more than 100 flights Wednesday in the Northeast, said spokeswoman Brandy King.
Maryland Governor Martin O'Malley wants people to stay off the roads.
"This is a serious traffic hazard and challenge," O'Malley said at a press briefing from the state's operation center in Hanover.
Maryland officials said 1,600 maintenance workers and 1,400 pieces of equipment would be on the roads all night battling the storm.