Miami - Hurricane Irma gave Florida a coast-to-coast pummelling with winds up to 200km/h on Sunday, swamping homes and boats, knocking out power to millions and toppling massive construction cranes over the Miami skyline.
The 640km-wide storm blew ashore in the mostly cleared-out Florida Keys, then marched up its western coast, its punishing winds extending clear across to Miami and West Palm Beach on the Atlantic side.
Irma was nearing the heavily populated Tampa-St Petersburg area late on Sunday, though in a much-weakened state. While it arrived in Florida a Category 4 hurricane, by nightfall it was down to a Category 2 with winds of 160kph. Meanwhile, more than 160 000 people waited in shelters state-wide as Irma headed up the coast.
There were no immediate reports of deaths in Florida. In the Caribbean, at least 24 were people were killed during Irma's destructive trek.
Bryan Koon, Florida's emergency management director, said late on Sunday that authorities had only scattered information about the storm's toll, but he remained hopeful.
"I've not heard of catastrophic damage. It doesn't mean it doesn't exist. It means it hasn't gotten to us yet," Koon said.
In the low-lying Keys, where a storm surge of over three metres was recorded, appliances and furniture were seen floating away, and Monroe County spokesperson Cammy Clark said the ocean waters were filled with navigation hazards, including sunken boats. But the full extent of Irma's wrath there was not clear.
The county administrator, Roman Gastesi, said crews would begin house-to-house searches on Monday to check on survivors. And an airborne relief mission, led by C-130 military cargo planes, was gearing up to bring emergency supplies to the Keys.
Storm surge was a big concern. The National Hurricane Center said a federal tide gauge in Naples reported a two metre rise in water levels in just 90 minutes late on Sunday.
Miami - Hurricane Irma slammed into the Florida Keys Sunday, lashing the tropical island chain with fearsome wind gusts as it churns towards the US state's west coast where a mass exodus has turned cities into ghost towns.
Many streets were flooded in downtown Miami and other cities.
In downtown Miami, two of the two dozen construction cranes looming over the skyline collapsed in the wind. A third crane was reported down in Fort Lauderdale. No injuries were reported.
A Miami woman who went into labour was guided through delivery by phone when authorities couldn't reach her because of high winds and street flooding. Firefighters later took her to the hospital.
An apparent tornado spun off by Irma destroyed six mobile homes in Palm Bay, midway up the Atlantic coast. Flooding was reported along Interstate 4, which cuts across Florida's midsection.
Curfews were imposed in Miami, Tampa, Fort Lauderdale and much of the rest of South Florida, and some arrests of violators were reported. Miami Beach barred outsiders from the island.
Fort Lauderdale police arrested nine people they said were caught on TV cameras looting sneakers and other items from a sporting goods store and a pawn shop during the hurricane.
More than 3.3 million homes and businesses across the state lost power, and utility officials said it will take weeks to restore electricity to everyone.
While Irma raked Florida's Gulf Coast, forecasters warned that the entire state was in danger because of the sheer size of the storm.
7 million warned to evacuate
In one of the largest US evacuations, nearly seven million people in the Southeast were warned to seek shelter elsewhere, including 6.4 million in Florida alone.
About 30 000 people heeded orders to leave the Keys as the storm closed in, but an untold number refused, in part because, to many storm-hardened residents, staying behind in the face of danger is a point of pride.
John Huston, who stayed in his Key Largo home, watched his yard flood even before the arrival of high tide.
"Small boats floating down the street next to furniture and refrigerators. Very noisy," he said by text message. "Shingles are coming off."
Irma made landfall just after 09:00 at Cudjoe Key, about 32km outside Key West. During the afternoon, it rounded Florida's southwestern corner and hugged the coast closely as it pushed toward Naples, Sanibel, Fort Myers and, beyond that, Sarasota, at 23kph.
Forecasters warned some places could see a storm surge of up to five metres of water.
Gretchen Blee, who moved with her husband to Naples from Long Island, New York, after Superstorm Sandy in 2012 heavily damaged their beach home, took cover in a hotel room as Irma raged.
"I said, 'Let's go and live the good life in paradise'," she said. "And here we are."
Irma at one time was the most powerful hurricane ever recorded in the open Atlantic, a Category 5 with a peak wind speed of 300 kph, and its approach set off alarm in Florida.
For days, forecasters had warned Irma was taking dead aim at the Miami area and the rest of the state's Atlantic coast. But then Irma made a more pronounced westward shift — the result of what meteorologists said was an atmospheric tug-of-war between weather systems that nudged Irma's crucial right turn into Florida's Gulf Coast.