The day’s highest threat – a level 3 of 5 – exists for about 13.6 million of those people, in parts of Alabama, Tennessee, far western North Carolina and Georgia, including the Atlanta area, according to the prediction center.
A flood watch also is in effect for more than 2 million people in areas of Georgia and Florida Wednesday morning to Thursday morning. The forecast shows 2 to 4 inches of widespread rainfall is expected, with some isolated areas getting around 5 inches.
Conditions for the Southeast will begin to deteriorate as storms pop up as soon as the late morning, with storms becoming more consistent in the afternoon and continuing into the evening and early Thursday morning, CNN meteorologist Rob Shackelford said.
The storm system comes as parts of the region are still in recovery mode from recent consecutive severe weather events, including tornadoes and treacherous thunderstorms.
Monday and Tuesday brought a double-whammy of severe storms and dozens of tornado reports across Texas, Georgia, South Carolina, Mississippi and Alabama – downing trees and power lines as well as damaging homes and businesses.
The storms Tuesday killed at least one person in Georgia and another person in Texas, local officials said.
A man in East Texas was killed when a tree fell on an RV in the Whitehouse community, the Smith County emergency management coordinator said.
Another person died in Bryan County, Georgia, as severe weather swept through the area, local officials said. The county, which is near Savannah, declared a state of emergency due to the impacts of a tornado and set a curfew through early Wednesday morning, officials said.
An EF-2 tornado went through Johnson County, Texas, south of Fort Worth on Monday evening, the National Weather Service said. The NWS also confirmed an EF-1 tornado in Collin County and an EF-0 tornado in Johnson County.
A preliminary survey found four EF-1 tornadoes hit Mississippi on Tuesday, the NWS said.
Storm’s path across South
As the storm makes its way across the battered South, different areas will feel its effects at different times.
Beginning Wednesday around 10:30 am, the Atlanta metro area and the remainder of Georgia can expect to see the strongest possibility for tornadoes, damaging wind gusts and large hail, Shackelford said. These threats are expected to impact the state through midnight.
Later Wednesday, Nashville and parts of Alabama – including Montgomery and Birmingham – are also under the same triple-threat from 1 to 11 pm
As for the Carolinas, the greatest threats are tornadoes and damaging winds, with less of a possibility for hail compared to their neighbor states – though it can not be ruled out.
Charleston, South Carolina, can expect to see severe conditions beginning around 6 pm through early Thursday. Meanwhile, Charlotte and Raleigh in North Carolina may potentially see severe storms start around midnight, with improvements by 7 am Thursday.
Correction: An earlier version of this story overstated the number of people during the day’s most severe weather threat level. About 13.6 million people live in the area with that threat level.
CNN’s Robert Shackelford, Dave Alsup, Gene Norman, Rebekah Riess and Jason Hanna contributed to this report.