One of the most powerful storms to hit the United States swept through parts of Florida’s heavily populated Gulf Coast on Wednesday, causing widespread damage.

St. PETERSBURG, Fla. — Hurricane Jan left a path of destruction in southwest Florida, trapping people in flooded homes, causing damage the roof of the hospital intensive care units and knocking out power to 2 million people before targeting the Atlantic coast.

One of the strongest hurricanes to ever hit the United States swept across the Florida peninsula Wednesday night, threatening catastrophic flooding inland, the National Hurricane Center warned.

The center’s 2 a.m. advisory said Yang was expected to exit over Atlantic waters later Thursday, with flooding rains continuing across central and northern Florida.

In Port Charlotte, along Florida’s Gulf Coast, storm surge flooded a hospital’s lower-level emergency room even as high winds blew part of the roof off the intensive care unit, according to a doctor who works there.

Water poured into the intensive care unit, forcing staff to evacuate the hospital’s sickest patients, some of whom were on ventilators, to other floors, said Dr. Birgit Bodin of HCA Florida Fawcett Hospital. Employees used towels and plastic containers to try to mop up the soggy mess.

The medium-sized hospital occupies four floors, but due to damage, patients were confined to only two floors. Bodin planned to spend the night there in case people affected by the storm arrived and needed help.

“As long as our patients are OK and nobody dies or has a bad outcome, that’s the main thing,” Bodin said.

Law enforcement officials in nearby Fort Myers received calls from people trapped in flooded homes or worried relatives. Appeals were also posted on social media sites, some with videos showing debris-covered water sloshing up to the eaves of houses.

Brittany Hayler, a journalist from Pittsburgh, contacted emergency services about her mother in North Fort Myers, whose home was flooded with 5 feet (1.5 meters) of water.

“We don’t know when the water will fall. We don’t know how they are going to leave, their cars are broken,” Heiler said. “Her only way out is by boat.”

Hurricane Ian turned streets into rivers and downed trees on Wednesday as it slammed into southwest Florida with winds of 150 miles per hour (241 kilometers per hour), pushing up a wall of storm surge. Ian’s strength at landfall was Category 4, tying it for the fifth-strongest hurricane, measured by wind speed, to ever hit the U.S.

By Wednesday evening, Ian had weakened to a Category 1 storm with winds of 90 mph (144 kph) as it moved over land. However, storm surges of up to 6 feet (2 meters) were expected on the opposite side of the state, in northeast Florida, on Thursday.

The storm was about 55 miles (90 km) southwest of Orlando with maximum sustained winds of 75 mph (120 kph) at 2 a.m. Thursday, the Miami Hurricane Center said.

A hurricane warning remained in effect north of Bonita Beach, about 31 miles (50 km) south of Fort Myers, to the Anclote River, including Tampa Bay, and from Sebastian Bay to the Flagler/Volusia county line.

The center has discontinued the hurricane warning between Bonita Beach and Chokoloski. A tropical storm warning from Chokoloska to Flamingo in the southwestern tip of the state has also been discontinued.

Hurricane-force winds are expected in central Florida through early Thursday, with widespread catastrophic flooding likely, the hurricane center said.

As of Wednesday evening, no deaths from Jan had been reported in the United States. But a boat carrying Cuban migrants sank in stormy weather east of Key West on Wednesday.

The US Coast Guard launched a search and rescue mission for 23 people and managed to find three survivors about two miles (three kilometers) south of the Florida Keys, officials said. Four other Cubans swam to Stock Island, east of Key West, the US Border Patrol said. Air crews continued to search for perhaps 20 remaining migrants.

Earlier, the storm hit Cuba, killing two people and knocking out the country’s electrical grid.

The eye of the hurricane hit Cayo Costa, a barrier island west of the heavily populated Fort Myers. As it approaches, waters discharged from Tampa Bay.

More than 2 million homes and businesses in Florida are without power, according to Almost every home and business in the three counties was without power.

Sheriff Bull Prummel of Charlotte County, north of Fort Myers, imposed a curfew from 9 p.m. to 6 a.m. “in order to save life,” saying violators could be charged with a second-degree felony.

“I am imposing the curfew as a means of protecting the people and property of Charlotte County,” Prummel said.

Weather Underground predicted the storm would pass near Daytona Beach and enter the Atlantic before coming back ashore in South Carolina on Friday.

The governors of South Carolina, North Carolina, Georgia and Virginia have preemptively declared states of emergency. Forecasters predicted Ian would return to those states as a tropical storm, likely to bring more flooding rains over the weekend.

Associated Press contributors include Cristina Mesquita in Havana, Cuba; Cody Jackson and Adriana Gomez Licon in Tampa, Florida; Frida Frisar in Miami; Anthony Izaguirre in Tallahassee, Florida; Mike Schneider in Orlando, Florida; Seth Borenstein and Aamer Madhani in Washington; Bobby Cain Calvan in New York; Andrew Welsh-Huggins in Columbus, Ohio; Jay Reeves in Birmingham, Alabama and Alina Hartunian in Phoenix, Arizona.