Florida scrambles ahead of Irma landfall

As southern Florida falls under hurricane warnings, petrol shortages and gridlock have plagued thousands of people fleeing for high ground ahead of Irma.

More than 500,000 people have been ordered to leave as the category-five hurricane tracks towards the state and that volume has turned usually simple trips into tests of will.

Carmen Pardo and her six-year-old daughter, Valeria, drove around Miami for seven hours frantically searching for somewhere to fill their petrol tank. They found nothing.

She eventually booked the only flight she could find leaving the city, to Orlando, where she reserved two seats on a bus bound for Tallahassee on Friday.

Late on Thursday, the National Hurricane Center issued the first hurricane warnings for the Keys and parts of southern Florida, including some of the Miami metropolitan area.

People along the Atlantic coast anxiously watched as Irma battered the northern Caribbean, killing at least 11 people and leaving thousands homeless.

At least 31,000 people fled the Florida Keys, which could begin seeing wind and rain from Irma as early as Friday night, Governor Rick Scott said.

With winds that peaked at 300km/h, Irma has been the most powerful hurricane ever recorded in the Atlantic.

NASA secured Kennedy Space Center, closing its doors to all non-essential staff, and SpaceX launched an unmanned rocket for an experimental flight.

Georgia Governor Nathan Deal has ordered evacuations and authorised about 5000 National Guard members to help with response and recovery.

The last category-five storm to hit Florida was Andrew in 1992, which killed 65 people and inflicted $US26 billion in damage.