(CNN) — Hurricane Ian’s vicious combination of winds, rain and storm surge caused at least a dozen deaths, flooded homes, cut off roadways and left millions of Florida residents without power Thursday.

And the storm’s path of destruction is not over. Ian made landfall Wednesday afternoon in southwest Florida and has since been downgraded to a tropical storm, but the storm is dropping heavy rain on central and northeast Florida throughout Thursday. Ian is forecast to strengthen to a Category 1 hurricane and make a second landfall in South Carolina on Friday, the National Hurricane Center said.

In southwest and central Florida, at least 15 people were reported dead so far due to the storm.

The death toll in Charlotte County, Florida, was at least eight or nine, Charlotte County Commissioner Joseph Tiseo told CNN’s Alisyn Camerota Thursday afternoon. About five people are believed to have died in Lee County, the sheriff there said.

One person who was in hospice care died in Osceola County, Emergency Management Director Bill Litton said. And a 72-year-old man in Deltona died overnight after going outside to drain his swimming pool during the storm, according to the Volusia County Sheriff’s Office.

“This could be the deadliest hurricane in Florida’s history,” President Joe Biden said Thursday. “The numbers are still unclear, but we’re hearing early reports of what may be substantial loss of life.”

Florida residents assessing storm damage Thursday found collapsed buildings, ongoing flooding, downed power lines and impassable roads, including a key bridge connecting Sanibel and Captiva islands to Florida’s mainland that has been washed out. More than 2.6 million electric customers have no power Thursday, according to PowerOutage.US, and some drinking water systems have broken down completely or have boil notices in effect.

“I just literally got out of a helicopter where I was able to take a complete tour of the entire county and there’s really no words that I can say to tell you what I’ve seen,” Lee County Sheriff Carmine Marcino said on CNN Thursday. “The Fort Myers Beach area, buildings, major, major homes and buildings completely washed away with vehicles in the water, vehicles in the bay, boats are upside down.”

Emergency responders conducted rescues by air, land and boat to save people trapped by the floodwaters. As of 2 p.m. Thursday, more than 500 people have been rescued in Charlotte and Lee counties, the Florida Department of Emergency Management said in a tweet. In Orlando, emergency responders navigating a street-turned-river told CNN’s Don Lemon they had conducted at least 200 rescues since early Thursday morning.

The rescue efforts come a day after Ian came ashore near Cayo Costa as a Category 4 hurricane with 150-mph winds, making it one of the strongest storms ever to make landfall on Florida’s west coast. The storm cut a path from near Fort Myers in the southwest across to the eastern part of the state, and its combination of wind, rain and storm surge caused flooding that Gov. Ron DeSantis called “a 500-year flood event.”

Here are the latest developments:

• Tropical storm status: Ian weakened to a tropical storm Thursday with winds of 70 mph, and the center of the storm was about 40 miles northeast of Cape Canaveral around 2 p.m. ET, the National Hurricane Center said. Based on wind speed, Ian tied with 2004’s Hurricane Charley as the strongest storm to make landfall on the west coast of the Florida Peninsula, both with 150-mph winds at landfall.

• Hurricane warnings for South Carolina: Hurricane warnings are in place for the entire coast of South Carolina. In addition, Tropical Storm warnings are in place from Jupiter, Florida, up the east coast to Duck, North Carolina.

• Record-high storm surges: Ian’s storm surge hit up to 12 feet in some places in western Florida. On Thursday morning, a storm surge warning — meaning life-threatening surges could hit — was in place for a coastal stretch from northeastern Florida into an area north of Charleston, South Carolina.

• More than a foot of rainfall: Lehigh Acres near Fort Myers got 14.42 inches of rain, and Warm Mineral Springs near Port Charlotte got 11.05 inches. Up to 30 inches of rain may have fallen in parts of Florida by storm’s end, forecasters say.

Rescue teams navigate waters to free trapped residents

Sunrise on Thursday gave Florida residents their first look at Ian’s overnight wrath — and the results were not pretty.

As Ian pushed inland, ocean water piled up onshore Wednesday — 12 feet in some places — and 150-mph winds whipped. 911 call centers in several counties were inundated.

Scott Carlos, who rode out the storm in his fourth-story Fort Myers condo, saw waves of water crash into homes across the street, up to their roofs, he said. Roads are littered Thursday with washed-out vehicles, he told CNN on Thursday.

“Everybody’s garages basically just gave out. … Cars are everywhere, smashed up in the street. There’s debris everywhere,” he said.

As Ian continues trudging northeast, heavy rain and flooding has been reported in the Orlando area, where 8 to 12 inches of rain had already fallen and up to 4 more inches of rain was expected. In Orlando, a reporter for CNN affiliate WESH rescued a woman after seeing her trying to drive through floodwaters, carrying her on his back in waist-high water to dry ground, WESH video showed.

In Fort Myers — where about 90% of electric customers were without power — Fire Chief Tracy McMillion told residents to stay inside, and to stay hopeful. “We’re coming for you, be encouraged,” he told residents Wednesday night.

The city’s downtown streets were flooded Wednesday with almost 4 feet of water, Mayor Kevin Anderson told CNN.

Thomas Podgorny was trapped in his two-story home in Fort Myers with three others, watching vehicles float away outside and worrying about others who did not evacuate, he told CNN Wednesday evening.

“I’ve lost my house. I have water and gas flowing through my bottom floor,” he said. “My neighbors have very little breathing room in their one-story house.”

One couple there was trapped in their home when the ceiling caved in.

“Something is dripping on me,” Belinda Collins recalled her partner saying. “He got up, and the ceiling — the family room ceiling — caved in.” They called 911 and were waiting for a call back about when it would be safe to leave, they said.

In Port Charlotte, the storm tore off the roof above a hospital’s ICU with patients inside Wednesday, forcing staff to move them to a post-operation recovery area, Dr. Birgit Bodine, an internal medicine specialist at the facility, told CNN.

Water gushed down stairwells to other floors, and other patients needed to be moved either to beds in hallways or to a different, dry wing of the hospital.

“We still have water in hallways that we’re still sloshing through,” but patients are safe in dry beds, and as many as possible were transferred to the dry wing, Bodine told CNN Thursday morning.

People in nearby Collier County, which includes Naples, were also trapped in their homes, calling for help, after electricity went out. In Naples, half the streets were not passable Wednesday because of high water, officials said.

“Some are reporting life threatening medical emergencies in deep water. We will get to them first. Some are reporting water coming into their house but not life threatening. They will have to wait. Possibly until the water recedes,” the Collier County Sheriff’s Office said Wednesday evening.

Complicating matters, neighboring Lee County’s 911 system was down and calls were being rerouted to Collier County, Chief Stephanie Spell told CNN. “At this point the majority of our 911 calls are water rescues,” Spell added.

In Sarasota County, sheriff’s deputies and fire crews had a backlog Thursday morning of more than 500 calls for help to respond to, the county sheriff’s office said. Deputies were “responding to the highest priority calls” that still were in the queue Thursday morning, the office said.

Monster storm leaves ‘life-changing’ mark on Florida

Even before the hurricane made landfall, officials knew the damage would be severe, and there will be a long road to recovery.

“Ian is going to be a life-changing event. This is a very powerful, catastrophic storm that is going to do significant damage,” President and CEO of Florida Power & Light Eric Silagy, said.

Some sections of infrastructure will be irreparable and need to be rebuilt — which can take weeks, Silagy said.

In Fort Myers Beach, key drinking water equipment failed, town spokesperson Jennifer Dexter told CNN.

“When the backup water pump system goes down, that shows you how serious it is,” she said.

Punta Gorda’s water system is empty and boil-water notices are in effect, according to an update from the city overnight.

Lee County Utilities issued a systemwide boil-water notice for all customers effective immediately due to the impacts of the hurricane, according to county officials. Residents in parts of Pasco County were also asked to boil their tap water as the water distribution system in the area lost pressure and a water main ruptured.

In Manatee County, residents were asked to limit flushing, showering, doing dishes and laundry due to power outages impacting the system.

In Cape Coral, authorities were getting reports of significant structural damage across the city, Ryan Lamb, the city’s fire chief and emergency management director, told CNN.

Gov. DeSantis has asked President Joe Biden to approve a major disaster declaration for all 67 counties in the state, his office said in a news release. DeSantis is also asking Biden to grant FEMA the authority to provide 100% federal cost share for debris removal and emergency protective measures for the first 60 days from Ian’s landfall.