Video: Thousands trapped in homes as intensified Category 4 hurricane Ian swamps Florida

Hurricane Ian, one of the most powerful storms ever recorded in the US, swamped southwest Florida on Wednesday, turning streets into rivers, knocking out power to 2 million people and threatening catastrophic damage further inland.

A coastal sheriff's office reported that it was getting many calls from people trapped in flooded homes. Desperate people posted to Facebook and other social sites, pleading for themselves or their loved ones to be rescued. Some video showed debris-covered water sloshing toward homes’ eaves.

The storm surge flooded a lower level emergency room in Port Charlotte, while fierce winds tore part of its fourth floor roof from its intensive care unit, according to a doctor who works there.

Water gushed down from above onto the ICU, forcing staff to evacuate the hospital’s sickest patients — some of whom were on ventilators — to other floors, said Dr Birgit Bodine of HCA Florida Fawcett Hospital. Staff members used towels and plastic bins to try to mop up the sodden mess.

The medium-sized hospital spans four floors, but patients were forced into just two because of the damage. Dr Bodine planned to spend the night at the hospital, in case people injured from the storm arrive there needing help.

“The ambulances may be coming soon and we don’t know where to put them in the hospital at this point because we’re doubled and tripled up,” she said.

“As long as our patients do OK and nobody ends up dying or having a bad outcome, that’s what matters.”

The hurricane's centre made landfall near Cayo Costa, a barrier island just west of heavily populated Fort Myers. As it approached, water drained from Tampa Bay.

Mark Pritchett stepped outside his home in Venice around the time the hurricane churned ashore from the Gulf of Mexico, about 55km to the south. He called it “terrifying.”

“I literally couldn’t stand against the wind,” Pritchett wrote, in a text message.

“Rain shooting like needles. My street is a river. Limbs and trees down. And the worst is yet to come.”

On Wednesday, a boat carrying Cuban migrants sank in the stormy weather in waters east of Key West. The US Coast Guard initiated a search and rescue mission for 23 people and managed to find three survivors about two miles 3km south of the island chain, officials said.

Four other Cubans swam to Stock Island, just east of Key West, the US Border Patrol said. Air crews continued to search for possibly 20 remaining migrants.

The Category 4 storm slammed the coast with 241m/h winds and pushed a wall of storm surge accumulated during its slow march over the Gulf. More than 2 million Florida homes and businesses were without electricity, according to a website named PowerOutage. Nearly every home and business in three counties was without power.

The storm previously tore into Cuba, killing two people and bringing down the country's electrical grid.

About 2.5 million people were ordered to evacuate southwest Florida before Ian hit, but by law no one could be forced to flee.

News anchors at Fort Myers television station WINK had to abandon their usual desk and continue storm coverage from another location in their newsroom because water was pushing into their building near the Caloosahatchee River.

Though expected to weaken to a tropical storm as it marches inland at about 14km/h, Ian's hurricane force winds were likely to be felt well into central Florida. Hours after landfall, top sustained winds had dropped to 170km/h, making it a Category 2 hurricane. Still, storm surges as high as 2 metres were expected on the opposite side of the state, in northeast Florida.

Sheriff Bull Prummell of Charlotte County, just north of Fort Myers, announced a curfew between 9pm and 6am “for life-saving purposes”, saying violators may face second-degree misdemeanour charges.

“I am enacting this curfew as a means of protecting the people and property of Charlotte County Prummell said.

Jackson Boone left his home near the Gulf coast and hunkered down at his law office in Venice with employees and their pets. Boone at one point opened a door to howling wind and rain flying sideways.

“We’re seeing tree damage, horizontal rain, very high wind,” Boone said by phone.

“We have a 50-plus-year-old oak tree that has toppled over.”