South Carolina Gov. Henry McMaster said conditions are "very dangerous" as Ian comes ashore, but so far the amount of water in places like the hospital district of Charleston is lower than expected.

"But I would ask people: Don't quit yet because this is still coming. We're not out of the woods," McMaster said.

South Carolina has positioned 90 National Guardsmen for high-water vehicle support. They have received a few requests for support, including for swift water rescue teams, said Kim Stenson, the head of South Carolina Emergency Management.

Stenson said they expect calls for damage and flooding to increase throughout the day.

A tornado threat is increasing as Hurricane Ian gets closer to the coast of the Carolinas.

Myrtle Beach and Greenville, South Carolina; Wilmington, North Carolina and Virginia Beach, Virginia, are all under tornado watch through 10 p.m.

A tornado warning is also in effect south of Wilmington.

-ABC News' Melissa Griffin

President Joe Biden pledged the U.S. would do "whatever it takes," to help Florida recover from Hurricane Ian, stressing the effort would be done as "one nation and one America," during an event at the White House marking the Jewish New Year.

"We're working very closely with the governor and the entire Florida delegation, Democrat and Republican, making sure that we can do everything we can, including now search and rescue, recovery and rebuilding efforts, but it’s going to go on for a long while. And whatever it takes, we’re going to be there, as one nation, and one America. We're not going to walk away," Biden said.

Biden noted the time of celebration is also a "very difficult time for so many Jewish families in Florida," and those with loved ones in the state.

"[O]ur heart goes out to everyone there in the state experiencing what could be maybe one of the most devastating hurricanes in the history of that state," Biden said.

-ABC News' Molly Nagle

President Joe Biden spoke with South Carolina Gov. Henry McMaster Friday ahead of Hurricane Ian's expected landfall.

Biden told McMaster the administration will provide whatever assistance South Carolina needs. Biden issued an emergency declaration for South Carolina Thursday night.

-ABC News' Molly Nagle

The U.S. Department of Health and Human Services has declared a public health emergency for the state of Florida.

HHS Secretary Xavier Becerra made the declaration Monday to address the possible health impacts for Florida residents once Hurricane Ian nears the state.

"We will do all we can to assist Florida officials with responding to the health impacts of Hurricane Ian," Becerra said in a statement. "We are working closely with state, local, and tribal health authorities, as well as our federal partners, and stand ready to provide additional public health and medical support."

HHS has pre-positioned two 15-person health and medical task force teams from its National Disaster Medical System, as well as a 13-person incident management team and two pharmacists to assist with the response in Florida.

"These teams are highly trained and ready to respond if, when, and where they may be needed following the storm," HHS Assistant Secretary for Preparedness and Response Dawn O’Connell said.

Florida Gov. Ron DeSantis declared a state of emergency on Saturday. That declaration was approved by President Joe Biden on Sunday.