Tropical Storm Helene barreled across the southeastern United States on Friday, killing around 20 people and causing widespread destruction and flooding.

Helene crossed Florida's northwest coast as a Category 4 hurricane on Thursday with windspeeds of 140 miles per hour (225 kilometers per hour), generating a massive storm surge and cutting off power to millions of homes in multiple states.

Helene later weakened to a tropical storm, but officials warned the storm continued to be "extremely dangerous" as it moved to the Carolinas and Georgia.

At least 11 people died in Georgia alone. Governor Brian Kemp said dozens of people were still trapped in damaged buildings.

Authorities were "having a hard time getting to places" so teams with chainsaws were "working to free up roads," Kemp told a news conference.

At least six people died in South Carolina, two in Florida and two in North Carolina. Cities as far inland as Atlanta, Georgia, were hit with flooding from the heavy downpour. In North Carolina, residents near Lake Lure Dam were urged to evacuate to escape an "imminent" dam failure.

The US National Hurricane Center warned residents to shelter from "catastrophic winds," storm surge and rainfall. "This is an extremely dangerous and life-threatening situation," the center said. 

Helene one of largest storms ever to hit Gulf Coast 

Helene was unusually large for a Gulf of Mexico hurricane.

Airports in the Florida cities of Tampa, Tallahassee and St. Petersburg remained closed early Friday, while hundreds of flights in Charlotte, North Carolina, and Atlanta, Georgia, were delayed or canceled, according to the tracking website FlightAware.com.

More than 4 million homes and businesses were without power in Florida, Georgia and South Carolina on Friday morning.

The governors of those states as well as Alabama and Virginia all declared emergencies.

Florida Governor Ron DeSantis mobilized the National Guard and ordered thousands of personnel to ready for search-and-rescue operations.

In Georgia, Governor Kemp also mobilized an additional 1,000 National Guard troops, on top of the 500 he mobilized earlier.

US President Joe Biden urged people to heed official evacuation warnings.

"I urge everyone in and near the path of Helene to listen to local officials and follow evacuation warnings," he said. "Take this seriously, and be safe."

Where is Helene headed next?

On Friday morning, Helene was moving north with windspeeds of 45 miles per hour (75 kilometers per hour), the National Hurricane Center in Miami reported.

Forecasters said the storm would continue to weaken as it moves into Tennessee and Kentucky.

Helene is expected to bring heavy rain to the Appalachian Mountains, potentially triggering mudslides and flash flooding.

Helene was the eighth named storm of the Atlantic hurricane season, which began in June.

mfi,kb/msh (AFP, AP)