Ian, the first hurricane to make landfall in South Carolina since Matthew in 2016, has not caused any deaths in South Carolina, Gov. Henry McMaster said Saturday.

“Another good story for South Carolina, and we’re open for business,” he said at a news conference.

Ian barreled through South Carolina on Friday. The hardest-hit areas were along the coast from Charleston to Horry County, said Kim Stenson, director of the South Carolina Emergency Management Division. Charleston saw 6 to 8 inches of rain.

The remnants of Hurricane Ian, once a Category 4 hurricane that made multiple U.S. landfalls, are pushing up the mid-Atlantic and bringing widespread rain from Virginia to Connecticut.

Ian is now considered a post-tropical cyclone with maximum sustained winds of 35 mph.

Flood watches are in effect in Virginia and West Virginia, where up to 6 inches of rain is expected through Saturday afternoon. A wind advisory is also in effect; gusts could reach 50 mph at higher elevations.

The rain will then continue to move north. Some of the Northeast coast, especially Delaware and Long Island, could see up to 6 inches of rain over the next 48 hours.

-ABC News’ Kenton Gewecke

President Biden has declared that an emergency exists in North Carolina and ordered federal assistance to help with the state's response in the aftermath of Hurricane Ian.

"The President’s action authorizes the Department of Homeland Security, Federal Emergency Management Agency (FEMA), to coordinate all disaster relief efforts which have the purpose of alleviating the hardship and suffering caused by the emergency on the local population," the White House said in a statement released early Saturday.

FEMA is authorized to identify, mobilize and provide equipment and resources to help the recovery efforts on the ground.

"Deanne Criswell, Administrator, Federal Emergency Management Agency (FEMA), Department of Homeland Security, named John F. Boyle as the Federal Coordinating Officer for Federal recovery operations in the affected areas," said the White House."

Ian’s winds have come down to 50 mph as the storm continues to move north as a post-tropical cyclone.

Ian will continue to weaken as it moves north, and will bring heavy rainfall in short periods of time through the morning hours, prompting flood watches to be issued from North Carolina to West Virginia.

Sanibel, Florida Mayor Holly Smith said that her city will not be the same following Hurricane Ian's catastrophic impact.

Smith said she was on the island for four hours Friday and witnessed the devastation firsthand.

"Unless you're on the ground, you really can't take in the gravity of what we experienced. It's a different Sanibel," Smith told ABC News Live Prime.

Smith said that she was checking in on 300 residents and that it was very important to make contact.

"As far as we know at this point, the number of fatalities recorded are four,'' Smith said.

"This is going to be a very long recovery process," Smith added of the efforts to get everybody off the island and to safety. "It's not habitable."

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