The governor of Florida urges people “not risk your life or the lives of your loved ones”, as the “catastrophic storm” approaches.
Around 5.6 million Florida residents have been ordered to evacuate the state as Hurricane Irma gets closer.
The category five storm has already moved through the Caribbean and the British Virgin Islands, killing at least 22 people and leaving a trail of destruction in its wake.
The deadly hurricane carries winds of up to 155mph and could travel from one end of Florida to the other when it is expected to hit near Key West early on Sunday.
Its path could also take in Georgia and South Carolina.
Forecasters adjusted the storm’s potential path more toward the west coast of Florida, away from the Miami metropolitan area of 6 million people, meaning “a less costly, a less deadly storm,” University of Miami researcher Brian McNoldy said.
LIVE: ‘Go now’, Florida governor says as Hurricane Irma approaches
However, they warned that the strong winds were so wide they could reach from coast to coast.
“This is a storm that will kill you if you don’t get out of the way,” National Hurricane Centre meteorologist Dennis Feltgen said.
“Everybody’s going to feel this one.”
As residents tried to evacuate in their droves, motorways became gridlocked and petrol stations were inundated.
Manny Zuniga was on the road for 12 hours trying to reach Orlando from his home in Miami – a journey which usually takes four hours.
“We’re getting out of this state… Irma is going to take all of Florida,” he said.
More than a quarter of the state’s population was ordered to leave, one of the largest-scale evacuations in its history.
Experts say Hurricane Irma could be the most serious test of Florida’s storm endurance since Hurricane Andrew in 1992, which damaged 125,000 homes and killed 40 people.