At least seven people have been killed by tornadoes in Georgia and Alabama and local officials expect the death toll to increase.
In Georgia, local TV reported that a five-year-old died after a tree fell on a car in Jackson.
More than 35 tornadoes were reported by the National Weather Service across the southern US on Thursday, putting more than 30 million people at risk.
The storms have caused blackouts for thousands of people in four states.
More than 147,000 residents in Alabama, Georgia, Tennessee and the Carolinas were without power yesterday evening.
Severe weather is forecast to continue overnight.
The governors of Alabama and Georgia have each signed state of emergency declarations.
On the opposite side of the country, California has been pummelled by a series of severe storms that have caused flooding, mudslides and power outages. At least 18 people have died there due to the severe weather.
After a brief respite Thursday, officials in California say more storms are forecast to pick up Friday night and over the weekend.
