ATLANTA >> Tropical Storm Helene brought life-threatening flooding to the Carolinas today after causing widespread destruction as a major hurricane moving through Florida and Georgia overnight, killing at least 20 people, swamping neighborhoods and leaving more than 4 million homes and businesses without power.

Helene hit Florida’s Big Bend region as a powerful Category 4 hurricane on Thursday at 11:10 p.m. ET (5:10 p.m. Hawaii time) and left a chaotic landscape of overturned boats in harbors, felled trees, submerged cars and flooded streets.

Police and firefighters carried out thousands of water rescues throughout the affected states, including in Atlanta, where an apartment complex had to be evacuated due to flooding.

Helene came ashore in Florida with 140 mph (225 kph) winds, weakening to a tropical storm as it moved into Georgia early today. It was carrying maximum sustained winds of near 45 mph (97 kph) as of 11 a.m. and was forecast to stall over the Tennessee Valley through the weekend.

Life-threatening storm surges, winds and heavy rains continued, the NHC said. The National Weather Service issued flash flood warnings for several counties in Georgia, South Carolina and North Carolina this morning.

“This is a PARTICULARLY DANGEROUS SITUATION. SEEK HIGHER GROUND NOW!” the service said.

In western North Carolina, Rutherford County emergency officials warned residents near the Lake Lure Dam just before noon to immediately evacuate to higher ground, saying “Dam failure imminent.”

In nearby Buncombe County, landslides forced interstates 40 and 26 to close, the county said on X.

The extent of the damage in Florida began emerging after daybreak.

In coastal Steinhatchee, a storm surge – the wall of seawater pushed ashore by winds – of eight to 10 feet (2.4-3 meters) moved mobile homes, the NWS said on X. In Treasure Island, a barrier island community in Pinellas County, boats were grounded in front yards.

The city of Tampa posted on X that emergency personnel had completed 78 water rescues of residents and that many roads were impassable because of flooding. The Pasco County sheriff’s office rescued more than 65 people overnight.

The U.S. Coast Guard said it had saved nine people from storm waters. Video posted online showed a Coast Guard crew pulling a man and his dog wearing life vests from the ocean on Thursday after his sailboat became disabled off Sanibel Island.

Kevin Guthrie, Florida’s emergency management director, urged residents in the affected areas to stay off the roads.

“I beg you, do not go out,” Guthrie said at a morning press briefing. “We have 1,500 search and rescue personnel in the impacted areas. Please get out of the way so we can do our jobs.”

Officials had pleaded with residents in Helene’s path to heed evacuation orders, describing the storm surge as “unsurvivable,” as NHC director Michael Brennan warned.

In Taylor County, the Sheriff’s Department wrote on social media that residents who decided not to evacuate should write their names and dates of birth on their arms in permanent ink “so that you can be identified and family notified.”

Some residents had stubbornly stayed put.

Ken Wood, 58, a state ferry boat operator in Pinellas County, said he should have heeded evacuation orders rather than riding out the storm at home with his 16-year-old cat, Andy.

“I’ll never do that again, I swear,” Wood said. “It was a harrowing experience. It roared all night like a train. It was unnerving. The house shook.”

Down the hill from his house, the storm flooded some homes with chest-deep salt water. One house caught fire and burned down, shooting 30-foot flames in the stormy sky, he said.

“Old Andy seemed like he didn’t care,” Wood said. “He did fine. But next time we leave.”

Some of Wood’s neighbors were not as fortunate. Pinellas County Sheriff Bob Gualtieri said first responders were unable to answer several emergency calls from residents overnight due to the conditions. County authorities today found at least five people dead.

Georgia Governor Brian Kemp cited 11 storm-related fatalities in his state so far. At least two people died in South Carolina when trees fell on their homes, local media reported.

Helene was unusually large for a Gulf hurricane, forecasters said, though a storm’s size is not the same as its strength, which is based on maximum sustained wind speeds.

A few hours before landfall, Helene’s tropical storm winds extended outward 310 miles (500 km), according to the National Hurricane Center. By comparison, Idalia, another major hurricane that struck Florida’s Big Bend region last year, had tropical storm winds extending 160 miles (260 km) about eight hours before it made landfall.

Airports in Tampa, Tallahassee and St. Petersburg suspended operations on Thursday and remained closed early today. Hundreds of flights into and out of Charlotte, North Carolina, and Atlanta were delayed or canceled, according to the tracking website FlightAware.com.

More than 4 million homes and businesses were out of power in Florida, Georgia and the Carolinas, with tens of thousands more facing outages in Virginia, Tennessee and Kentucky, according to the tracking website Poweroutage.us.

Reinsurance broker Gallagher Re said preliminary private insurance losses could reach $3 billion to $6 billion, with additional losses to federal insurance programs approaching a potential $1 billion.