Wind gusts close to hurricane force are battering islands in Florida’s south as Hurricane Irma is due to hit the mainland in the coming hours.
Water levels are already rising on the coast of the US state where a huge storm surge is expected.
Some 6.3 million people had been told to evacuate, but the state governor said on Saturday it was now too late to leave for anyone remaining.
At least 24 people have died after Irma earlier hit several Caribbean islands.
With maximum sustained winds of 120mph (193km/h), Irma hurricane has now weakened to a category three hurricane after making landfall in Cuba’s north-east late on Friday, the National Hurricane Center (NHC) says in its latest advisory at 03:00 GMT on Sunday.
But Irma is expected to strengthen and will remain a powerful hurricane as it approaches Florida, the NHC says.
It warns that a “life-threatening storm surge” is expected in the Florida Keys – a chain of small islands in Florida’s south – and also the west coast of Florida.
Irma is predicted to hit the coast on Sunday morning, but the outer bands are already affecting the south of the state and central Miami is being lashed by heavy rain.
The Florida Keys have suffered some minor damage and are expected to bear the brunt of the storm in the coming hours.
The head of emergencies agency Fema, Brock Long, told CNN there were “no safe areas within the Keys”.
“You put your life in your own hands by not evacuating,” he added.
“If you’re in an evacuation zone, you’ve got to get to a shelter need to get to a shelter… there’s not many hours left”, Florida Governor Rick Scott warned residents.
“The winds are coming, there is not gonna be a lot of time now to be able to drive very far.”
Thousands of people on the mainland are currently without electricity.
The western Gulf coast is expected to be worst affected, with cities such as Tampa and St Petersburg in the path of the storm.
The Tampa Bay area, with a population of about three million, has not been hit by a major hurricane since 1921.
Gov Scott said storm surges in coastal areas could be as high as 15ft (4.6m), adding that people “cannot survive this”.
He said that storm surges in coastal areas could be as high as 12ft (3.7m), adding that people “cannot survive this”.
Some 50,000 people have gone to shelters throughout the state, the governor said. Media reports say shelters in some areas have been filling up quickly and some people have been turned away.
Miami city and Broward county have imposed curfews to help clear the roads of traffic. -BBC