Helene unleashed devastation across the Southeast.
More than 230 people have been killed from Hurricane Helene, which unleashed devastation across Florida, Georgia, South Carolina, North Carolina, Virginia and Tennessee.
Helene, which made landfall in Florida's Big Bend region as a massive Category 4 hurricane, has become the deadliest mainland hurricane since Katrina in 2005.
Helene has strengthened to a Category 1 hurricane with sustained winds of 80 mph.
Helene -- now located about 500 miles south-southwest of Tampa, Florida -- is the fifth hurricane to form in the Atlantic Basin this season.
Sixty-four out of Florida’s 67 counties are under alerts as Helene nears the state, said Kevin Guthrie, executive director of the Florida Division of Emergency Management.
Only three counties -- Escambia, Okaloosa and Santa Rosa -- are not under some type of watch or warning, like tropical storm, storm surge or hurricane, he said.
Wednesday is the last day for Floridians to finalize preparations before Helene hits, Florida Gov. Ron DeSantis warned.
All Floridians should be prepared for power outages, DeSantis added.
At least 12 health care facilities, including hospitals and nursing homes, are evacuating, and more may choose to do so in the coming hours, the governor said.
-ABC News’ Alex Faul
Extreme flash flooding is possible in the Blue Ridge Mountains in Georgia, North Carolina and South Carolina.
First, a storm system separate from Helene is hitting the south on Wednesday. Up to 6 inches of rain is possible over the next 24 hours, bringing a flash flood risk from Atlanta to Asheville, North Carolina.
Then, Thursday afternoon through Friday morning, Hurricane Helene will bring even more extreme rain and flooding to the southern Appalachians.
A rare "high risk" alert for heavy rain has been issued. Up to 15 inches of rain is possible in some spots.
-ABC News’ Max Golembo
Helene is forecast to bring 10 to 15 feet of dangerous storm surge to Florida’s Big Bend area, and 4 to 8 feet of storm surge to Tampa Bay.
In 2005, during Hurricane Katrina, at least 1,500 people died "directly, or indirectly, as a result of storm surge," according to the National Hurricane Center.
Click here to read how storm surge works and why it's so dangerous.
