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

The weakening hurricane has now been downgraded from a category four to a category one storm, but it remains formidable after its landfall on Florida's west coast Wednesday afternoon as a Category 4 hurricane. Reports say that Floridians have been warned that the most dangerous 24 hours lay ahead and the mayor of Tampa has urged people to shelter in place through the night into Thursday morning.

The storm slammed the coast with 150 mph (241 kph) winds and pushed a wall of storm accumulated during its slow march over the Gulf of Mexico. More than 2 million Florida homes and businesses were without electricity, according to PowerOutage.us. Nearly every home and business in three counties was without power.

So far, there has been no official reports of storm-related fatalities or serious injuries, but 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 rescue for themselves or loved ones. Some video showed debris-covered water sloshing at homes' eaves.

The storm surge flooded a hospital's 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.

Mark Pritchett stepped outside his home in Venice around the time the hurricane churned ashore from the Gulf of Mexico, about 35 miles (55 kilometers) 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."

A boat carrying Cuban migrants sank Wednesday in the stormy weather in waters east of southwest Florida's Key West island. The U.S. Coast Guard initiated a search and rescue mission for 23 people and managed to find only three survivors about two miles south of the island chain, officials said. Four other Cubans swam to Stock Island, just east of Key West, the U.S. Border Patrol said. Air crews continued to search for the remaining migrants.

Ian was forecast to weaken further as it crossed the Florida peninsula on a northeasterly track, and was expected to reach the Atlantic Coast on Thursday afternoon, possibly as a tropical storm, according to the National Hurricane Center(NHC).

But Ian remained a potent force. Up to 30 inches (76 cm) of rain was forecast to fall on parts of central Florida, the NHC said. 

Flash floods were possible all across Florida. Hazards include the polluted leftovers of Florida's phosphate fertilizer mining industry, more than 1 billion tons of slightly radioactive waste contained in enormous ponds that could overflow in heavy rains.

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

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

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

(All images via VCG, with input from AP and Reuters)

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