Civilians and officials in Florida are rushing to prepare for the arrival of Hurricane Irma, or crawling through highway gridlock to try to escape the path of a record-breaking storm that has already devastated much of the Caribbean.

The state has called called on 5.6 million people to evacuate, or more than one quarter of the state’s population, according to state emergency officials.

US President Donald Trump called Irma “a storm of absolutely historic destructive potential” in his weekly address to the nation, and Florida’s officials are becoming increasingly desperate in their pleas for residents to leave.

“We are running out of time. If you are in an evacuation zone, you need to go now. This is a catastrophic storm like our state has never seen,” Florida Governor Rick Scott said, adding that the storm’s effects would be felt from coast to coast in the state.

The warning came after the head of the US’s federal emergency agency said the storm could “devastate” the US.

“Hurricane Irma continues to be a threat that is going to devastate the United States in either Florida or some of the south-eastern states,” said Brock Long of the Federal Emergency Management Agency (FEMA).

“The entire south-eastern United States better wake up and pay attention,” he added.

A mild wind in South Florida was swaying palm trees and bushes on Friday evening, but with Irma predicted to directly hit Miami about 20 miles from Hollywood that calm will not last long. Irma was due to lash Cuba and the Bahamas on Friday evening as it rolled towards the US.

Most houses at this point have boarded up their windows with timber or corrugated metal, creating an apocalyptic atmosphere that contrasts with the still-bright Miami sunshine that beat down for most of the day.

People are making long walks to their nearest market to get final supplies – officials have encouraged people to prepare for up to six days of isolation – hoping to conserve on petrol, since shortages are producing long lines at the pump or closing stations entirely after they run dry.

For those staying in town, radio DJs are warning that final preparations should be made by Friday evening.

Mandatory evacuations have already been ordered along the potential path of the hurricane, in Miami-Dade County, all of Palm Beach Island, parts of Broward County, and Monroe County, where Key West is located. Mandatory evacuations have also been issued in coastal Georgia as well adding to the exodus of millions.

Andrew Sussman, Florida's hurricane programme manager, said that the total of more than five million asked to leave includes people throughout the southern half of the state as well as those living in inland Florida in substandard housing who were also told leave.

Government buildings left abandoned after Hurricane Irma destruction

More than a dozen shelters have been opened in southern Florida counties, and radio reports noted on Friday afternoon that some were already reaching capacity. Officials, eyeing that strain on resources, have rushed to open up more. More than 6,000 people have so far taken up the offer of shelter by Friday afternoon.

Irma is expected to make landfall near Miami on Sunday morning, after roughly a day of tropical wind storms pounding down on the area. The storm has already left at least 21 people dead from its path of destruction through the Caribbean, and officials and experts are worried that it could lead to one of the biggest natural disasters in US history.

As the now category 4 hurricane moved west toward Cuba, winds slowing slightly to 155mph, Mr Scott once again painted a desperate picture for Floridians.

“It is wider than our entire state and could cause major and life-threatening impacts on both coasts, coast to coast,” he said during a press briefing. “Regardless of which coast you live on, be prepared to evacuate.”

Barbuda, Hurricane Irma – in pictures Show all 7 1 /7 Barbuda, Hurricane Irma – in pictures Barbuda, Hurricane Irma – in pictures A roof-less house in Barbuda ABS TV Barbuda, Hurricane Irma – in pictures A mobile network tower snapped in two by the hurricane ABS TV Barbuda, Hurricane Irma – in pictures The hurricane left debris strewn across the island Barbuda, Hurricane Irma – in pictures Rubble in the aftermath of the hurricane ABS TV Barbuda, Hurricane Irma – in pictures The destruction in Barbuda, as seen from an ABS TV helicopter ABS TV Barbuda, Hurricane Irma – in pictures As well as destroying most houses, the hurricane also left plenty of flooding ABS TV Barbuda, Hurricane Irma – in pictures Barbudan residents survey the damage ABS TV

Mr Scott has issued a state of emergency for the entire state, and has ordered all 6,000 of the state’s national guardsmen to be on duty to respond to any complications that may arise related to the storm.

Petrol shortages and gridlock plagued the evacuations, turning normally simple trips into tests of will. Highways north were bumper-to-bumper, while very few cars and tractor-trailers drove on the south lanes.

Manny Zuniga left his home in Miami at midnight on Thursday, planning to drive through the night to avoid the traffic gridlock that he’d seen on television. It still took him 12 hours to get 230 miles to Orlando – a trip that normally takes four hours. Mr Zuniga is headed for a relative’s house in Arkansas with his wife, two children, two dogs and a ferret.

“We’re getting out of this state,” he said, filling up the petrol tank of his tightly packed SUV in Orlando. “Irma is going to take all of Florida.”

Kenneth Weipert, a stranded tourist from Scotland said he had made multiple attempts to book a flight, with no luck.

“We have never been through anything like this before and we are quite worried about it... We are in the hotel and the hotel is hurricane-proof, allegedly,” he added.

Tony Marcellus was another who was struggling to figure out how to get his elderly mother and grandfather from their home near the ocean in West Palm Beach to his place in Atlanta, 600 miles away. Flights and rental cars were sold out, so he told the associated Press that he hired an Uber driver to take them 170 miles to meet him in Orlando.

Mr Trump, eyeing what could be the second major natural disaster of his presidency, praised the work of the Federal Emergency Management Agency on Thursday, and said that the National Guard had saved more than 14,000 lives in Texas, where Hurricane Harvey brought devastating winds and rains last week as the first major hurricane to make landfall in the continental US in more than 10 years.

“I can say this: Florida is as well prepared as you can be for something like this, and now it’s just a question of what happens,” Mr Trump said. “It’s the largest hurricane we’ve ever seen coming out of the Atlantic, and the winds are the strongest that we’ve ever seen from a hurricane in the region.”