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.

President Joe Biden spoke with Florida Gov. Ron DeSantis Thursday morning to discuss support for the state in response to Hurricane Ian and the disaster declaration the president approved overnight, White House press secretary Karine Jean-Pierre said in a tweet.

"The President told the Governor he is sending his FEMA Administrator to Florida tomorrow to check in on response efforts and see where additional support is needed. The President and Governor committed to continued close coordination," she wrote in a tweet.

Biden first spoke to the governor, a leading political opponent of Biden and possible 2024 Republican presidential candidate, on Tuesday after several days of questions about whether the two would connect.

-ABC News' Justin Gomez

Hurricane Ian caused extensive and "historic" impact and damage in across Florida, Gov. Ron DeSantis said at a press conference Thursday.

"The impacts of this storm are historic and the damage that was done has been historic and this is just off initial assessments. There's going to be a lot more assessing that goes on in the days ahead," DeSantis said.

"But I think we've never seen a flood event like this. We've never seen storm surge of this magnitude and it hit an area where there's a lot of people in a lot of those low-lying areas and it's going to end up doing extensive damage to a lot of people's homes," he said.

As of 6 a.m., there are 2.02 million customers without power, according to DeSantis.

DeSantis said Charlotte and Lee counties are "basically off the grid at this point." The areas will likely need a rebuilding of their infrastructure.

Ian, now a tropical storm, is near Florida’s east coast and is moving back over water. Ian is expected to re-intensify and could be at near-hurricane strength when it approaches the coast of South Carolina on Friday.

A hurricane watch has been issued for South Carolina and the Georgia coast.

Ian is producing catastrophic flooding over east-central Florida and is expected to produce life-threatening flooding, storm surge and gusty winds across portions of Florida, Georgia and the Carolinas.

There are already more than 14,000 customers without power in Georgia.

-ABC News' Max Golembo