The latest fatality is a Tennessee woman who died when a tree fell on her home as storms moved through the state Tuesday.
Two people died in Georgia in severe storms Monday that sent trees onto a vehicle and home.
Severe weather that rolled through Texas was headed to Alabama, Georgia and the Florida Panhandle, forecasters said.
"It's a daily thing that is affecting us, because obviously, we're working with the weather on a daily basis," one farmer said.
The 129-foot commercial vessel left port with 19 people on board. Six have been rescued.
ERCOT, which previously came under fire after February's deadly winter storm, issued the watch Tuesday.
"The tornado took the house," according to an official in a Louisiana parish where one person died.
Alex Epstein, author of "The Moral Case for Fossil Fuels," blamed failures on the state's embrace of wind and solar energy.
More than 7 inches of rain caused flooding in Nashville over the weekend.
The city of almost 700,000 remained under a flash flood warning Sunday morning.
More severe weather was forecast through Sunday in parts of the region.
Newnan, southwest of Atlanta, was damaged by an overnight tornado that struck its downtown. One person in Coweta County died from a medical emergency.
One person was killed during Friday's storm in Coweta County, Georgia. Alabama authorities previously said 5 people were killed in that state.
Health officials are continuing to investigate the causes of deaths that may be related to the winter storm disaster that paralyzed the state in February.
Strong and long-lived tornadoes, hail the size of baseballs or larger and damaging winds in excess of 75 mph are all possible Thursday across the South.