Latest forecast
Hurricane Helene is forecast to make landfall as a major hurricane between 9:30 p.m. and 11:30 pm. Thursday in Florida's Big Bend region.
Because Helene is a very large hurricane, it will impact nearly all of Florida.
Helene is set to bring catastrophic storm surge up to 20 feet to the Big Bend area. Four to 8 feet of storm surge is expected around Tampa Bay.
The major 110 mph winds will cause widespread tree damage and power outages across the Florida Panhandle and the Big Bend area.
Tornado watches are in effect for most of Florida and parts of Georgia and South Carolina through Thursday night.
By Friday morning, Helene will weaken to a tropical storm as it moves north through Atlanta with heavy rain and strong winds.
Georgia should be prepared for hurricane-force wind gusts to cause damage and power outages.
Rainfall totals from Helene will be 6 to 12 inches, with locally up to 20 inches in some areas.
Catastrophic and life-threatening flash flooding, as well as significant landslides, are expected across portions of the southern Appalachians through Friday. There is an extreme flood risk from Tallahassee, Florida, to Atlanta to Asheville, North Carolina.
-ABC News' Melissa Griffin