The National Hurricane Center issued a hurricane warning for the entire coast of South Carolina. A hurricane watch had been in place for the entire state earlier.

Now a tropical storm, Ian is expected to become a hurricane again Thursday night before making landfall near Charleston, South Carolina, on Friday morning or early afternoon.

Ian currently has maximum sustained winds of 70 mph, just 4 mph from returning to hurricane strength.

After conducting initial safety assessments, Hillsborough County Administrator Bonnie Wise has removed the evacuation order in place.

After hosting more than 8,000 evacuees across 47 shelters, the county is preparing to conclude its sheltering operations or transition shelter availability for evacuees who continue to need assistance.

"Residents whose homes have been damaged are encouraged to find a safe place to stay. That place might be with family, friends, or at a nearby hotel," the county said in a statement.

The county also urged residents heading home to drive with caution, not to drive through obstructions or standing water and to stay away from downed power lines.

-ABC News' Alexandra Faul

The Federal Emergency Management Agency's search and rescue teams have been out in the field since 4 a.m. Thursday, FEMA Administrator Deanne Criswell told "Good Morning America." It will prioritize saving lives and helping people impacted by the storm, who may be trapped.

Criswell said FEMA has been hearing reports of people calling 911 through the night and will use information it has gathered in those hours to prioritize rescues in harder-hit areas.

"This has been just a catastrophic storm and it's left significant damage in its path," Criswell said.

Criswell said FEMA will be able to conduct rescues by land, air and sea.

The most significant impacts have been happening in Lee County, where people are without power and water. Criswell also expects impacts across the western coast of Florida.

"Water is dangerous. Even though the storm has passed, the water that is there is still dangerous. There's debris, there's chemicals, there could be downed power lines. People need to be careful, they need to stay vigilant," Criswell said.

There is potentially major flooding in Orange and Seminole counties and St. Johns River, potentially up to Jacksonville in northeast Florida, Gov. Ron DeSantis said Thursday.

"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. And I know Seminole County has done evacuations, I know they've opened shelters, but we're gonna see a lot of images about the destruction that was done in southwest Florida and obviously we have massive assets there," DeSantis said.

"This storm is having broad impacts across the state and some of the flooding you're going to see in areas hundreds of miles from where this [storm] made landfall are going to set records. And that's going to obviously be the things that will need to be responded to," DeSantis added.

The damage caused by the storm will likely take years to repair, he said.

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

Tropical Storm Ian has weakened slightly, but it is expected to not only strengthen but rapidly intensify overnight as it travels over warm waters in the Caribbean.

As of 5 p.m. ET, the storm system had maximum sustained winds of 45 mph and was moving west-northwest at 12 mph, with the center located about 220 miles away from Grand Cayman.

Dry air ahead of the storm has delayed the strengthening trend so far. But the rapid intensification is expected to occur Monday into Tuesday as the system continues across the northwestern Caribbean and closes in on western Cuba.

Over the next 24 hours, the outer bands will impact Jamaica and the Cayman Islands, bringing rounds of heavy rain, possible flash flooding and storm surge. Later Monday and into Monday night, Ian will be closing in on western Cuba and will likely bring significant wind and storm surge impacts to the region.

A hurricane warning is in effect for Grand Cayman and portions of western Cuba. A tropical storm watch has been issued for portions of western Cuba, as well as the lower Florida Keys, including Key West.

As of 5 p.m., the forecast track was nudged slightly eastward. Overall, the forecast guidance variability and uncertainty will remain high, and the track for where the storm will be from the middle to the end of the week will continue to shift over the next 24 to 48 hours.

-ABC News' Dan Peck