Ian, now a post-tropical cyclone, was weakening but still forecast to bring treacherous conditions to parts of the Carolinas, Virginia and West Virginia into Saturday morning, according to the National Hurricane Center.
"The dangerous storm surge, flash flooding and high wind threat continues," it said.
The storm struck Florida's Gulf Coast on Wednesday, turning beach towns into disaster areas, before hitting wind speeds of 85 mph (140 kph) as it pummeled waterfront Georgetown, north of the historic city of Charleston in South Carolina on Friday.
Roads were flooded and blocked by trees while a number of piers were damaged.
Around 1.9 million homes and businesses were without power in the Carolinas and Florida at 21:30 ET (01:30 GMT), according to tracking website PowerOutage.us.
Both the number of casualties and repair costs remain unclear, but as Florida entered its third day after Ian first hit, the extent of the damage was becoming apparent.
There have been reports of at least 21 deaths, Kevin Guthrie, director of the state's Division of Emergency Management, said at a morning briefing on Friday, stressing that some of those remained unconfirmed.
Some 10,000 people were unaccounted for, he said, but many of them were likely in shelters or without power.
"Those older homes that just aren’t as strong built, they got washed into the sea," said Governor Ron DeSantis.
"If you are hunkering down in that, that is something that I think would be very difficult to be survivable."
Meanwhile, insurers are bracing for a hit of between $28 billion and $47 billion, in what could be the costliest Florida storm since Hurricane Andrew in 1992, according to U.S. property data and analytics company CoreLogic.
U.S. President Joe Biden has already approved a disaster declaration, making federal resources available to counties impacted by the storm.
"We're just beginning to see the scale of that destruction. It's likely to rank among the worst ... in the nation's history," he said.
"DEVASTATING"
Fort Myers, a city close to where the eye of the storm first came ashore, absorbed a major blow, with numerous houses destroyed.
Offshore, Sanibel Island, a popular destination for vacationers and retirees, was cut off when a causeway was rendered impassable.
Hundreds of beleaguered Fort Myers residents lined up at a Home Depot on Friday on the east side of the city, hoping to purchase gas cans, generators, bottled water and other supplies. The line stretched as long as a football field.
Rita Chambers, a 70-year-old retiree who was born in Jamaica and has lived in Fort Myers since 1998, said Ian was unlike any storm she had ever seen.
"And I've been in hurricanes since I was a child!" said Chambers, who moved to New York as a teenager.
At a mobile home park on San Carlos Island in Fort Myers Beach, trailers had been pushed together by the wind and water. A boat, the "Dreamin,'" lay on its side at a local marina, where another boat had come to rest in a tree.
Deborah Grool, 70, lost her home and vehicles to the storm.
"This is devastating, because it's not just homes, it's businesses," said Grool, a real estate agent who has lived on the island for 45 years.
Meanwhile hundreds of miles north in Georgetown, residents were also trying to put their lives back together.
With a population of about 10,000, the town is a tourist destination known for its oak-lined streets and more than 50 sites on the National Registry of Historic Places. It was heavily damaged by 1989's Hurricane Hugo.
A city-commissioned report released in November 2020 found that about 90% of all residential properties were vulnerable to storm surge flooding.
Len Cappe, 68, a retired property manager who moved to Charleston two years ago, said Ian was the first big storm he has encountered.
"It's the wind, it rattles you," Cappe said. "It's blowing furiously."
Read more:
Maps-Hurricane Ian batters the Gulf Coast
Drone video shows boats washed ashore in Hurricane Ian's wake
A Florida town rebuilt after one hurricane endures another
Hurricane hunter says Ian's eyewall flight was 'worst I've ever been on'
How hurricanes cause dangerous, destructive storm surges
(Reporting by Brad Brooks in Fort Myers and Jonathan Drake in Charleston; Additional reporting by Sharon Bernstein and Kanishka Singh; Writing by Costas Pitas; Editing by Cynthia Osterman and Daniel Wallis)
