The second wintry storm in two weeks to hit the normally warm southern US has encrusted the region in ice, killing at least 11 people and knocking out electricity to hundreds of thousands of homes and businesses.
The deaths included three people who were killed when an ambulance careened off an icy Texas road and caught fire, the AP news agency reported.
Forecasters warned of more than 2.5cm of ice possible in some places on Wednesday. Snow was forecast overnight, with up to 7.6 cm possible in Atlanta and much higher amounts in the Carolinas.
President Barack Obama declared a disaster in South Carolina and for parts of Georgia, opening the way for federal aid.
In Myrtle Beach, South Carolina, palm trees were covered with a thick crust of ice.
The storm did not cause the widespread highway problems in Atlanta that the last storm did, largely because people had learned their lesson. Streets and highways were largely deserted.
Atlanta was caught unprepared by the last storm on January 28, when thousands of children were stranded all night in schools by less than less than 8cm of snow and countless drivers abandoned their cars.
The storm is seen moving northwards, threatening to bring more than 30 cm of snow on Thursday to the mid-Atlantic and northeast.
States of emergencies
Governors declared states of emergencies from Louisiana to New Jersey, and hundreds of schools, colleges and offices throughout the region shut down.
A basketball game between arch rivals Duke University and the University of North Carolina was called off.
More than 3,300 flights were cancelled and about 2,800 delayed on Wednesday, according to flight-tracking website FlightAware.com.
Another 3,700 flights were cancelled for Thursday, with about half of the flights to and from Washington and New York called off.
Hardest hit were Hartsfield-Jackson International Airport in Atlanta and Charlotte Douglas International Airport in North Carolina.
The US Department of Energy reported that 363,000 power customers were without electricity as of mid-afternoon.
More than a third of them were in Georgia, where some residents may have to wait up to a week for power to be restored, said Georgia Power spokeswoman Amy Fink.