Tropical Storm Helene brought life-threatening flooding to the Carolinas on Friday after causing wide destruction through Florida and Georgia overnight, killing at least five people, swamping neighbourhoods 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 11:10pm ET (0310 GMT on Friday), and left a chaotic landscape of overturned boats in harbours, 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 225 kmph winds, weakening to a tropical storm as it moved into Georgia early on Friday. It was carrying maximum sustained winds of 97 kmph as of 8 am and was forecast to continue shuffling northwards 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.

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 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.