A severe winter storm that whipped up tornadoes in the southern US has brought heavy snow to the Midwest and threatens disruption in the east.
At least six people have been killed and authorities have told people to stay at home rather than brave freezing temperatures and treacherous roads.
A state of emergency has been declared in Mississippi and Alabama after the storm downed power lines.
Hundreds of flights have been grounded by snow and blizzards.
More delays are expected as the storm moves towards New York state and Maine, where as much as 18 inches (46 cm) of snow is expected in the next 24 hours.
The National Weather Service has warned of near-zero visibility in Buffalo, New York, where heavy snowfall is predicted to combine with high winds.
Weather warnings are in place from Florida and the Gulf Coast all the way up to New England.
Little Rock, Arkansas, saw its first snow on Christmas Day in 83 years, while in neighboring Oklahoma seven inches of snow was blamed for a 21-vehicle pile-up on an interstate highway outside Oklahoma City.
Thirty-four tornadoes were reported in the southern states of Texas, Louisiana, Mississippi and Alabama on Tuesday. A large section of a church roof in Mobile, Alabama, was ripped off by a twister.
Falling trees claimed the lives of two people in Texas and Louisiana. Deaths were also reported on the roads in Oklahoma and Arkansas.
More than 200,000 people are said to be without power.