The aftermath of a deadly winter storm paralyzed much of the eastern United States today and forecasters warned of the worst cold in two decades from another arctic front this week.
The storm dumped snow and spread ice from New England into the Carolinas after battering the Midwest and Ohio Valley.
Temperatures hit -34C in Saranac Lake, New York, according to the National Weather Service.
States of emergency were declared from Mississippi to the District of Columbia, and the federal government shut down in Washington after about 13cm of snow.
School was called off in West Virginia, the Washington DC, area, parts of Kentucky and much of North Carolina.
Another Arctic front from the Great Lakes to the southern Great Plains will sweep to the eastern US coast by Thursday, the National Weather Service said.
Temperatures in the middle Atlantic states and Carolinas could reach lows not seen since the mid-1990s.
North Carolina Governor Pat McCrory urged residents to stay off ice-covered roads.
"The extended low temperatures ... and black ice will make this a very dangerous situation for several days," he said at a news conference.
At least six weather-related highway deaths were reported in Tennessee, Virginia and North Carolina.
Police worked through the night to clear a 19km backup of vehicles on icy Interstate 40 near Nashville.
Airlines cancelled about 1,600 US flights and commuter train service in northern Virginia was halted.
About 28cm of snow fell near Richmond, Virginia, and state police reported 1,035 accidents in 20 hours.
About 150 people gathered at Washington's Meridian Hill Park for a snowball fight sponsored by the Washington DC Snowball Fight Association.
"This weather's good, everybody's nice. So, lovin' it," Collin Lawrence, who was costumed as Marvel Comics' Captain America and plastered with snow, told Reuters Television.
Schools in Lexington, Louisville and several other Kentucky districts will be out again tomorrow.
Almost half the state's counties had declared emergencies, as well as 15 towns, the state Emergency Management Division said.
Officials in Ithaca, New York, pulled a pop-up window on its tourism page that had urged visitors to go to the Florida Keys instead.
"Please come back when things thaw out," it said.
In Maine, two 15-year-old boys spent a night out in -18C conditions when their snowmobile bogged down but were unharmed after taking shelter in a shed.
The intense cold forced the Pittsburgh Zoo to shut down until Friday.
