A resurgent Ian swept ashore on Friday afternoon near Georgetown, a waterfront town about 100 kilometres north of the historic city of Charleston, packing maximum sustained wind speeds of 140km/h as a category one hurricane, the US National Hurricane Center (NHC) said.
Roads were flooded with water and encumbered by trees while a number of piers were damaged as the storm left more than 400,000 homes and businesses in the Carolinas without power, according to the tracking website PowerOutage.us.
Ian, now classified as a post-tropical cyclone, would bring heavy rain and potential flash flooding to parts of North and South Carolina, Virginia and West Virginia until at least Saturday morning as it weakened, the NHC said.
The storm struck Florida's Gulf Coast on Wednesday as one of the most powerful storms ever to hit the US mainland and then cut a destructive path across the state, transforming beach towns into disaster areas with catastrophic flooding and winds.
There have been reports of at least 21 deaths in Florida, Kevin Guthrie, director of the state's Division of Emergency Management, said at a morning briefing. He stressed that some of those reports remained unconfirmed.
Georgetown, with a population of about 10,000, is a tourist destination known for its oak-lined streets and more than 50 sites on the National Registry of Historic Places. The town was heavily damaged by 1989's Hurricane Hugo.
Even before Ian's arrival, Charleston was seeing torrential rain. Video clips on social media showed several inches of water in some streets in the port city, which is especially prone to flooding.
A city-commissioned report released in November 2020 found about 90 per cent of all residential properties were vulnerable to storm surge flooding.
Two days after Ian first hit Florida, the extent of the damage there was becoming more apparent.
Some 10,000 people were unaccounted for, Guthrie said, but many of them were likely in shelters or without power. Roughly 1.6 million Florida homes and businesses remained without power on Friday, according to PowerOutage.us.
"You have homes just washing away," Governor Ron DeSantis said at a briefing on Friday in Lee County, which suffered widespread damage.
President Joe Biden, speaking at the White House, said the hurricane would likely rank among the worst in US history.
"We're just beginning to see the scale of that destruction," he said.
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 holidaymakers and retirees, was cut off when a causeway was rendered impassable.