The National Weather Service said near-blizzard conditions were recorded in parts of New York City, northeast New Jersey, the lower Hudson Valley and coastal Connecticut, CNN reported.
NBC News reported 468,000 homes and businesses, mostly in the South, without still without power heading into the night.
NBC said there were seven storm-related deaths in Texas, three in North Carolina, two each in Mississippi, Georgia and South Carolina, and one each in Virginia and New York.
Air travel was seriously disrupted, with more than 6,500 flight cancellations nationwide by 10:30 p.m. EST Thursday and another 4,000-plus flights delayed.
The network said the storm had deposited 10 inches of snow on New York City by Thursday afternoon after leaving at least a foot of snow behind in the Washington, D.C., and Baltimore areas overnight Wednesday. Similar amounts were expected to pile up in the Boston area and Philadelphia was covered in about 8 inches with schools already canceling classes for Friday in anticipation of another round of snow.
New Jersey Gov. Chris Christie declared an emergency for his state, where many schools called off classes Thursday.
New York Gov. Andrew Cuomo also declared a state of emergency for New York City, but schools there were open.
"New Yorkers should stay off of the roads and remain in their homes until the worst of the storm has passed," Cuomo recommended.
Police in New York said a private plow truck struck and killed a pregnant woman in Brooklyn Thursday. The woman, 36, was struck as she and her husband were putting groceries in their car, the Wall Street Journal reported.
She was taken to Maimonides Hospital, where an emergency Caesarian section was performed. The baby survived but was in critical condition, the newspaper said.
As the storm moved toward the northeast, forecasters said Philadelphia could get as much as 11 inches, New York may be blanketed with 15 inches and Boston could get 8 inches, forecasters said.
Further inland, areas from West Virginia through western Pennsylvania and western New York were expected to get 12 to 18 inches, AccuWeather said.
The Office of Personnel Management Federal ordered federal government offices closed in Washington Thursday, CNN said.
At its peak, the storm disrupted power for more than 772,000 customers in 14 states across the South and the District of Columbia, CNN reported. The majority of outages were in Georgia, and North and South Carolina.
As much as an inch of ice built up in Georgia and the Carolinas, felling trees and weighing down fragile power lines, NBC News said.
Philadelphia International, Newark (N.J.) Liberty International and Reagan International in Washington reported 48 percent to 68 percent of their air traffic was canceled.
Amtrak suspended some service in the Northeast, South and Mid-Atlantic regions Thursday.
Operation Blessing International, based in Virginia Beach, Va., said it has sent a team to the Charlotte-Concord, N.C., area to help people remove snow.