ST. PETERSBURG: Hurricane Ian trapped people in flooded homes in southwest Florida, damaged the roof of a hospital's intensive care unit and left 2 million people without power.

The National Hurricane Centre warned that one of the strongest hurricanes to ever hit the United States barreled across the Florida peninsula overnight Wednesday, threatening catastrophic flooding inland.

Ian was expected to emerge over Atlantic waters later on Thursday, with flooding rains continuing across central and northern Florida.

In Port Charlotte, on Florida's Gulf Coast, a hospital's low-level intensive care unit was flooded and part of the roof was blown off by strong winds, a doctor there said.

Patients in ICU and on ventilators were moved to higher floors.

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

Hurricane Ian turned streets into rivers and uprooted trees. Wind gusts of 150 mph (241 kph) hit southwest Florida on Wednesday. Ian is included in category 4. In terms of wind speed, it is the fifth strongest hurricane ever to hit the US.

Ian dropped in strength by late Wednesday to Category 1 with 90 mph (144 kph) winds as it moved overland. Still, storm surges as high as 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-based hurricane centre said.
A hurricane warning remained in effect north of Bonita Beach, about 31 miles (50 km) south of Fort Myers, to Anclote River including Tampa Bay and from Sebastian Inlet to the Flagler/Volusia county line.

Hurricane-force winds were expected across central Florida through early Thursday with widespread, catastrophic flooding likely, the hurricane centre said.

No deaths were reported in the United States from Ian by late Wednesday. But a boat carrying Cuban migrants sank Wednesday in stormy weather east of Key West.

The Weather Underground predicted the storm would pass near Daytona Beach and go into the Atlantic before veering back ashore in South Carolina on Friday.

The governors of South Carolina, North Carolina, Georgia and Virginia all preemptively declared states of emergency. Forecasters predicted Ian will turn towards those states as a tropical storm, likely dumping more flooding rains into the weekend.