Miami,  Hurricane Ian has caused significant damage to Florida while also claiming the lives of 10 people, with a warning now issued for the entire coast of South Carolina ahead of making landfall on Friday.

The US National Hurricane Center (NHC) said in its latest advisory issued late Thursday that Ian is now a tropical storm with maximum sustained winds of 110 km per hour, which is moving north-northeast at 15 km per hour, reports Xinhua news agency.

The storm, which made landfall in southwest Florida as Category 4 hurricane on Wednesday afternoon, regained hurricane strength on Thursday evening.

Coastal areas from Savannah River to Little River Inlet in South Carolina are under the hurricane warning.

The alert means that hurricane conditions are expected somewhere within the warning area.

Preparations to protect life and property should be rushed to completion.

"Major-to-record river flooding" will continue across central Florida through next week, according to the NHC advisory.

Considerable flash, urban, and river flooding is expected across coastal portions of northeast Florida, southeastern Georgia, and eastern South Carolina through Friday.

"The amount of water that's been rising and will likely continue to rise today, even as the storm is passing, is basically a 500-year flood event," Florida Governor Ron DeSantis told reporters on Thursday.

DeSantis added the damage caused by the storm to Florida will likely take years to repair.

"You're looking at a storm that's changed the character of a significant part of our state," he said.

"This is going to require not just emergency response now, in the days or weeks ahead. I mean, this is going to require years of effort to be able to rebuild and to come back."

The Sanibel Causeway, which connects Sanibel Island to Florida's mainland, has been damaged with portions washed away by storm surges.

As of Thursday, more than 2.6 million customers are without power in Florida due to the impact of the destructive storm, according to PowerOutage.us.

President Joe Biden spoke with DeSantis on Thursday morning about the federal assistance to the state in response to Ian, according to the White House.

Biden declared a major disaster exists in Florida earlier in the day and he and DeSantis committed to continued close coordination.

The President saysthat Ian could be the deadliest hurricane in Florida's history.