Tornado causes damage in North Texas
Around 8.5 million people from eastern Texas to northwestern Louisiana and southwestern Arkansas remain under tornado watches until 8 a.m. (9 a.m. ET).
Hail up to 1.5 inches in diameter and wind gusts to 75 mph are possible.
As the storm system moves east Tuesday, around 20 million people in the Lower Mississippi Valley and central Gulf Coast region will be under some threat of severe weather.
Major cities in the storm's path include Baton Rouge and New Orleans in Louisiana, and Jackson and Gulfport in Mississippi, along with Houston, Memphis and Birmingham, Alabama.
The potential for strong tornadoes continues into this evening, the Storm Prediction Center warned. "Tornadoes occurring at night are more than twice as likely to be deadly as those during the day."
About 18 million people from Texas to Alabama and north to Arkansas and Tennessee are under a flood watch Tuesday.