As the monstrous Hurricane Irma closes in on Florida's coast officials say that it will have a devastating impact on the majority of the state if it stays on its current trajectory.
Forecasters have calculated the storm's path is moving towards the west coast but the hurricane-force winds are so wide that Miami is still likely to see major destruction.
Irma has strengthened again as it barrelled between Cuba and the Bahamas and is once again a Category 5 storm, said news.com.au.
Category 5 is the highest classification used by meteorologists and denotes sustained wind gusts of more than 157mph (252km/h).
Irma was downgraded to a Category 4 Thursday but warm waters have fuelled its increase in wind speed.
A spokesman for the National Hurricane Center released a terrifying warning urging people to get out before it is too late.
Meteorologist Dennis Feltgen warned "This is a storm that will kill you if you don't get out of the way," as the massive hurricane hurls towards the coast.
Irma is expected to make landfall in the Florida Keys between 5am and 7am local time on Sunday.
"Everybody's going to feel this one," said Feltgen.
More than 5.6 million people have been asked to evacuate the state, with officials saying that it is now inevitable that Florida will caught in the path of the storm.
"It's not a question of if Florida's going to be impacted, it's a question of how bad Florida's going to be impacted," said administrator of the Federal Emergency Management Agency William "Brock" Long.
The National Weather Service has urged anyone remaining in the Keys, a string of islands to the south west connected to the mainland by a series of bridges, to heed evacuation orders.
"This is as real as it gets," they tweeted in a statement.
"Nowhere in the Florida Keys will be safe. You still have time to evacuate."
Officials are going door-to-door calling on people to evacuate.
While parts of Florida and Georgia are under a mandatory order to evacuate, officials are legally unable to forcibly remove anyone from their homes.
The death toll stood at 22 and was expected to rise as rescuers reached some of the hardest-hit areas.
And a new danger lay on the horizon to the east: Hurricane Jose, a Category 4 storm with 150kmkm/h (241km/h) winds that could punish some of the devastated areas all over again this weekend.
"I don't think it takes a rocket scientist to know that further damage is imminent," said Inspector Frankie Thomas of the Royal Police Force of Antigua and Barbuda.
Florida Governor Rick Scott is warning that residents in South Florida only have hours left to evacuate.
Scott on Friday told residents from seven counties that they should leave by midnight or should not get on the road.
"If you are planning to leave and do not leave tonight, you will have to ride out this extremely dangerous storm at your own risk," Scott said.
US President Donald Trump warned Americans to get out of the way of Irma.
"Hurricane Irma is of epic proportion, perhaps bigger than we have ever seen. Be safe and get out of its way, if possible. Federal G is ready!"
Florida Govenor Rick Scott said the call to evacuate had become even more dire.
"We're running out of time. The storm is almost here. If you are in an evacuation zone you need to go now," he said. "This is a catastrophic storm that our state has never seen. We can rebuild your home but we can't rebuild your life."
Hundreds of thousands of Floridians choked highways to race north, crowded airports and emptying supermarket shelves of bottled water and food, and draining petrol supplies to try to escape what authorities described as a "nuclear storm".
While many were heeding warnings that the entire state faces catastrophic damage, some Aussies were among those considering braving out the approaching hurricane.
Hurricane Irma is expected to rip into the state over the weekend. The looming threat of the dangerous storm has triggered a massive evacuation. Those trying to flee have encountered traffic jams and there have been fuel shortages, especially in south Florida.
Scott has urged Floridians for days to heed evacuation orders, but he has also told residents they don't need to leave the region, but instead to seek out nearby shelters.
Florida's major theme parks are planning to close as Hurricane Irma approaches the state.
Officials at Walt Disney World in Orlando announced Friday afternoon that its parks will close on Saturday and remain closed through Monday. Universal Orlando announced on its website that it will close at 7pm local time Saturday and will remain closed through Monday. Officials said they anticipate reopening on Tuesday.
SeaWorld in Orlando and Busch Gardens, which is in Tampa, also announced plans to shut down at 5pm local time Saturday and remain closed through Monday.
Irma has weakened from a Category 5 storm to Category 4 but is still blowing at a life-threatening 250km/h.
There are fears as well that it may strengthen again as it enters warmer than normal waters around Florida.
CUBA, BAHAMAS HIT BY IRMA
The storm churned in the Atlantic and has started to last Cuba and the Bahamas as it charts its path towards Florida.
The hurricane smashed homes, schools, stores, roads and boats on Wednesday and Thursday as it rolled over islands long known as turquoise-water playgrounds of the rich, including St. Martin, St. Barts, St. Thomas, Barbuda and Anguilla.
It knocked out power, water and telephone service, trapped thousands of tourists and stripped the lush green trees of leaves, leaving an eerie, blasted-looking landscape.
Authorities reported looting and gunfire in St. Martin, and a curfew was imposed in the U.S. Virgin Islands.
Meanwhile the US House voted to send a $US15.3 billion ($21b) aid package for Hurricane Harvey victims in Texas through to US President Donald Trump, which will extend US borrowing and fund government through to December 8.
Irma yesterday became the longest tropical cyclone in history to sustain wind speeds of 297km an hour. It is the most powerful Atlantic Ocean storm in recorded history.
And yesterday, it was also twice the size of the entire Florida peninsular.
While Hurricane Jose strengthened to an "extremely dangerous" Category 4 storm on Friday, according to the National Hurricane Centre.
Hurricane Katia has strengthened to a Category 2 storm in the Gulf of Mexico.
PRESIDENTS BAND TOGETHER TO HELP
All five living former US presidents have issued a joint One America Appeal for donations to support the staggering recovery needs from Hurricane Harvey that hit Texas.
Now that Hurricane Irma has damaged Puerto Rico and is closing in on Florida, the presidents are expanding the appeal to help its victims as well.
A website for tax-deductible donations related to both storms is now live at OneAmericaAppeal.org.
A special restricted account has been established through the George H.W. Bush Presidential Library Foundation to collect and quickly distribute donations to ensure 100 cents out of every dollar goes to assist hurricane victims.
The Carter Centre says Harvey has displaced more than one million people and caused an estimated $US180 billion ($248b) in damage over its 482-kilometre path of destruction.
Some forecasters have predicted that Irma's economic toll could be even greater.
Mr Trump tweeted that he was proud to stand with past presidents.
"We will confront ANY challenge, no matter how strong the winds or high the water. I'm proud to stand with Presidents for #OneAmericaAppeal," he tweeted.