Latest forecast
Helene, currently a Category 1 hurricane, is expected to rapidly intensify and could reach major category status -- Category 3 -- by Thursday morning.
Helene could be a high-end Category 3 hurricane with 125 mph winds by the time it makes landfall Thursday night in the Big Bend area of Florida. Helene might even be a Category 4 hurricane with 130 mph winds during landfall.
A hurricane warning is in effect just north of Tampa, covering Apalachicola, Florida; Tallahassee, Florida; and Valdosta, Georgia.
A tropical storm warning is in effect in Jacksonville, Florida; Orlando, Florida; Miami; and Charleston, South Carolina.
Inland flash flooding is also a major concern.
A separate storm is bringing heavy rain to Georgia and the Carolinas on Wednesday, so the additional rain from Helene could cause a historic flood event in the southern Appalachians Thursday night into Friday.
A tropical storm watch has been extended further north to include Atlanta and Asheville, North Carolina, for Thursday night into Friday morning. Strong, damaging winds up to 70 mph are possible in Atlanta on Friday.
-ABC News’ Max Golembo