Unseasonably warm weather across the eastern United States spawned a line of deadly storms in the Midwest and several south-central states and dropped heavy rain Thursday on the Atlantic Coast.

Tornadoes overnight Wednesday killed three people in Mississippi, two in Tennessee and one in Arkansas, according to local media.

Warm, humid air from the Gulf of Mexico colliding with colder, dryer air from Canada set off the violent weather.

The tornadoes damaged buildings, uprooted trees and left 8,000 homes without power in Mississippi.

Funnel clouds were spotted as far north as Illinois and Indiana, but no fatalities were reported.

There was a high chance of thunderstorms Thursday along the Gulf Coast in Louisiana, Mississippi, Alabama and Florida, as well as in neighbouring Georgia.

To the north-east, another cluster of severe weather along the same weather front was threatening potentially heavy thunderstorms in Virginia, Maryland and Delaware, as well as the US capital city, Washington.