Tropical Storm Helene brought life-threatening flooding on Friday to wide sections of the U.S. Southeast, where at least 43 people have been killed by a storm that swamped neighborhoods, triggered mudslides, threatened dams and left 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 (0310 GMT on Friday), and left a chaotic landscape of overturned boats in harbors, felled trees, submerged cars and flooded streets.

Florida Governor Ron DeSantis confirmed two storm-related deaths. Georgia Governor Brian Kemp said on X that two people in Wheeler County had died after a tornado touched down during the storm, and an ABC News affiliate reported that a firefighter was killed when a tree fell on his vehicle in Blackshear, Georgia.

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 on Friday. It was carrying maximum sustained winds of 60 mph (97 kph) as of 8 a.m. and was forecast to continue shuffling northward toward the Tennessee Valley.

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 on Friday morning.

“This is a particularly dangerous situation. Seek higher ground now!” the service said.

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 one of its helicopter crews saved a man and his dog 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 were staying stubbornly put.

“We’re under orders, but I’m going to stay right here at the house,” state ferry boat operator Ken Wood, 58, told Reuters before the storm from coastal Dunedin in Florida, where he planned to ride out the storm with his 16-year-old cat Andy.

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 on Friday. Hundreds of flights into and out of Charlotte, North Carolina, and Atlanta were delayed or cancelled, 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.