The remnants of Hurricane Ian drifted through Virginia early today, while storm-ravaged residents in Florida and the Carolinas faced a disaster recovery expected to cost tens of billions of dollars.

The storm's toll on human life also was expected to rise as floodwaters receded and search teams pushed farther into areas initially cut off from the outside world, seeking stranded survivors and the remains of anyone who may have perished.

At least 50 storm-related deaths have been confirmed since landed on Florida's Gulf Coast with catastrophic force on Wednesday as a Category 4 hurricane, packing maximum sustained winds of 240km/h.

Florida accounted for the bulk of fatalities, with 35 tallied by the sheriff's office in coastal Lee County, which bore the brunt of the storm when it made landfall, and 11 other deaths reported by state officials in four neighbouring counties.

US President Joe Biden and first lady Jill Biden will see the devastation in Florida first hand on Wednesday, the White House said in a statement late yesterday.

The Bidens will head first to Puerto Rico tomorrow, where hundreds of thousands of people were still without power two weeks after Hurricane Fiona hit the island.

North Carolina authorities said at least four people had been killed there. No deaths were immediately reported in South Carolina, where Ian made another landfall on Friday.

Cuba is restoring power after Ian knocked out electricity to the whole country of 11 million people, flattened homes and obliterated agricultural fields.

Chugging over land since then, Ian has diminished into an ever-weakening post-tropical cyclone.

The National Hurricane Center said heavy additional rainfall was possible across portions of West Virginia and western Maryland into this morning, even as "major to record flooding" was forecast to continue in central Florida.

Damage caused by Hurricane Ian on Sanibel Island

As the full scope of devastation came into clearer focus days after Ian struck, officials said some of the heaviest damage was inflicted by raging wind-driven ocean surf that rushed into seaside communities and washed buildings away.

Satellite images from the National Oceanic and Atmospheric Administration (NOAA) showed beach cottages and a motel that lined the shores of Florida's Sanibel Island had been demolished by storm surges. Although most homes appeared to still be standing, roof damage to all was evident.

Surveys from the ground showed that the barrier island, a popular tourist getaway that was home to some 6,000 residents, was left utterly devastated, from its infrastructure to its famously idyllic aesthetic character.

"It's all just completely gone," said Sanibel's city manager Dana Souza.

"Our electric system is pretty much destroyed, our sewer system has been damaged badly and our public water supply is under assessment."

The island's link to the mainland was severed by breaches to Sanibel's causeway bridge, further complicating recover yefforts, Ms Souza said.

People protest in Havana, Cuba, after Hurricane Ian knocked out power

After waning to a tropical storm by the end of its march across Florida to the Atlantic, Ian regained hurricane strength and pummelled coastal South Carolina on Friday, sweeping ashore near Georgetown, north of the historic port city of Charleston, with sustained winds reaching 140km/h.

Numerous roads were flooded and blocked by fallen trees while a number of piers were damaged in that area.

Even as they confronted a staggering amount of utility repairs and debris removal, authorities were busy searching for the missing.

As of Friday, some 10,000 people were reported unaccounted for in Florida, according to the state's emergency management director. He said many of those would likely turn out have merely been displaced and unreachable due to power and phone outages.

On Sanibel, crews were just making their way to the hard-hit east end of that island yesterday, "so our situation is that we're still in the search-and-rescue mode," Ms Souza said.

City officials were aware of nearly 300 households who failed to leave the island as the storm approached and whose whereabouts and well-being were now being checked, he said.

About 837,000 businesses and homes remained without power this morning in Florida alone, where more than two million customers lost electricity the first night of the storm.

In central Florida, heavy flooding from rain-swollen rivers and runoff appeared far more extensive than wind damage.

Insurers braced for between $28 billion and $47 billion in claims from what could amount to the costliest Florida storm since Hurricane Andrew in 1992, according to US property data and analytics company CoreLogic.