Hurricane Irma has now made landfall on Florida, slamming into Key West, bringing sustained winds of 130mph, as well as rain and threats of tornadoes in what is expected to be one of the worst storms to hit the area in living memory.
The state thought it had escaped the worst case scenario as the storm moved into land and was downgraded to Category 3 - but late Saturday night it re-energized and was upgraded back to Category 4, the second-worst level, with gusts of up to 144mph.
And this is only the beginning for the mainland US, as Irma is set to move inland northwest, threatening Naples and other cities up the west coast of Florida as the wears on.
A man was killed after tropical-storm-strength winds caused him to lose control of the truck he was driving through Monroe County, which contains Key West. He had been carrying a generator, local officials told ABC News.
Two others died in a car accident in Hardee County, Florida, the Florida Highway Patrol said. The area is around 60 miles inland from Sarasota.
And an elderly man died of natural causes while sheltering in a school in the city of Marathon on the Keys, Larry Kahn, an editor for FlKeysNews.com, said.
Those deaths come after Irma claimed at least 25 lives in the Caribbean as it swept over several countries, destroying entire islands.
Meanwhile, more than a million people have been left without power across the state, while storm surges of 10-15 feet have been predicted around the Everglades, where lower land exacerbates the floods.
Highs of 5-10 feet have been predicted in Miami, where at least one crane has been destroyed on a high-rise; although the cranes are built to withstand strong gusts, and act as weather vanes, swinging with the winds, Irma could prove too much for many.
Irma made landfall on the Florida Keys at around 9am, and continued to sweep over all of the islands, leaving terrified citizens hiding in shelters.
The city of Marathon was hit hard. Electricity and running water were both out at Marathon High School, which was set up to be one of four 'shelters of last resort'. But things were worse outside.
'Everything is underwater, I mean everything,' Kahn, one of those sheltering inside, said.
Meanwhile, food supplies were running low, and sheriff's deputies were searching the school's canteen for enough sustenance to keep the 50 or so people inside safe.
Another group is holed up in the Ernest Hemingway House in Key West, where the manager, 72-year-old Jacqui Sands, has elected to remain with the family's 54 six-toed cats and other members of staff.
The house is 16 feet above sea level, has 18-inch-thick limestone walls and three generators.
On the mainland, a crane atop a building - one of two dozen in the city - collapsed dramatically in the constant onslaught.
The weather service's Miami office said in a Tweet that one of its employees witnessed the crane boom and counterweight collapse in downtown Miami.
According to city officials, it would have taken about two weeks to move the cranes and there wasn't enough time.
As the hurricane moves up the west coast, experts have warned that there will be a negative surge of three or more feet, as water is pulled out into the sea.
That might look like the hurricane is subsiding - but it's just a prelude to the real surge, which will push huge amounts of water towards the land.
On Sunday, the National Weather Service (NWS) in Key West has issued stark warnings to Miami's residents, saying that emergency services - just a few of whom remain on the largely empty roads - would not be able to help anyone during the worst of the storm.
First responders are told to seek shelter as soon as winds reach 40mph or more, as safe movement through the streets becomes impossible.
The NEWS is also warning locals not to return to the city even when the winds move on - at least until authorities have given the all-clear that roads are safe for travel.
At 5:40am, the NWS said: 'Extreme, hurricane-force winds are imminent in the Lower Florida Keys. If you are here, please go to interior room away from windows.
Forecasts predict winds of up to 130mph and will rip through southern Florida as it travels between 6mph and 8mph up the western coast of the state.
Donald Trump sent a message to those caught up in the brutal hurricane, saying: 'This is a storm of enormous destructive power, and I ask everyone in the storm's path to heed all instructions from government officials.
Irma's outer bands pummeled Miami and parts of southeast Florida on Saturday afternoon. Two tornadoes hit Broward County after the National Weather Service issued a tornado watch.
There is also a deadly threat of 15ft storm surges with residents being urged not to return home given the enormous outer bands as emergency officials told those who had ignored evacuation orders that it was too late.
The National Weather Service had earlier warned that tornadoes were commonly spawned by a hurricane and could could damage far away from the center of the hurricane, while storm surges could cause more fatalities than any other hurricane hazard.
Around 6.3million people have been told to evacuate in anticipation of Irma and there are 70,000 people in evacuation shelters across Florida.
The state said Saturday that more than 400 shelters are open, mostly in schools, churches and community centers.
Time is running out for anyone who is now planning to leave, with Irma having arrived in parts of southern Florida, bringing heavy rain and strong wind gusts that make it impossible to drive.
An overnight curfew was imposed in Miami to stop opportunistic looters taking advantage of the countless coastal homes that now stand abandoned. The city had been on course for a direct hit but was thrown a sudden lifeline on Saturday when the storm changed course as it pounded Cuba.
More than 200,000 homes and businesses in Florida have lost power already. Florida Power and Light said on its website that more than half of those outages were in the Miami-Dade area, where about 600,000 people have been ordered to evacuate.
Residents in the Keys had been warned for days that they should pack up and leave before Irma hits. Some defiantly stayed, vowing to ride out the storm despite warnings that it may cost them their lives.
'The message has been clear - the Keys are going to be impacted, there is no safe area within the Keys, and you put your life in your own hands by not evacuating,' Long told CNN on Saturday.
The entire Florida Keys were supposed to be emptied and firefighters went door to door in mobile home parks, urging residents to get out. People who refused to evacuate were not being arrested, but were told they wouldn't be rescued once the storm arrives.
'You can call, but we're not coming,' Pinellas Sheriff Bob Gualtieri said.
Early on Sunday morning, footage started to emerge of Key West being battered by the storm.
Trash cans can be seen hurtling down the street in winds described as 'hurricane-like'. Trees have been ripped from the ground, crushing vehicles and properties, and sparks have started to fly from powerlines above quaint houses.
Many webcams set up for live streams of the city were wiped out before 6am as the hurricane neared.
Forecasts from the National Hurricane Center show that the impact of Hurricane Irma will stretch into Georgia, the Carolinas, Tennessee and Alabama.
A hurricane watch is in effect for the Georgia coast northward to Edisto Beach, South Carolina. Tropical storm warnings are in place along the Georgia and South Carolina coasts. Tropical storm watches also extend as far as eastern Alabama.
It can happen quickly and far from a storm's center, inundating areas that don't typically flood.
A storm surge doesn't just come from the ocean. It can come from sounds, bays and lakes, sometimes wells inland.
Large hurricanes tend to create a greater storm surge over a broader area, and coastal features such as bays can act like funnels and back water up into rivers and canals.
The National Hurricane Center forecasts water levels up to 15 feet above ground for the Florida Keys.
The Atlantic coast from Miami to Isle of Palms, South Carolina, could see up to 6 feet of storm surge.
About 1,000 miles of coastline from Tampa Bay to the mid-South Carolina coast could see storm surge.
So far Irma has claimed at least 25 lives after torturing the Caribbean. The death toll will likely rise as recovery missions continue.
There were no immediate reports of casualties in Cuba. Nine deaths were reported in the French Caribbean (St Martin and St Barthelemy), three in Puerto Rico, four in the US Virgin Islands, four in the British Virgin Islands, two on the Dutch side of St Maarten, one on Barbuda and one on Anguilla.
The storm toppled Cuba on Friday night and Saturday morning, pounding the island nation with 160mph winds and unprecedented rain.
Officials were desperate for anyone in the affected zones to get on the road before the conditions picked up on Saturday afternoon.
Some 7,000 National Guard troops were brought in to help deal with the catastrophe. People in Florida were being told to prepare three days' worth of food and water to ride out the storm.
Carl Roberts said he had Chinese food, a case of water and a million-dollar view in his 17th floor Gulf front condo, which is all he needed to weather the massive storm.
Carol Walterson Stroud figured Irma would turn elsewhere at first. Then, she didn't evacuate Key West because she's a nervous wreck driving alone, and her husband - 'a hard-headed conch' - wouldn't leave.
She is now hunkered down in a nearby senior center with her husband Tim, their granddaughter Sierra Costello, and dog Rocky. Her daughter, Breanna Vaughn, refused to leave her animals in her home a few blocks away.
The most threatening part of the storm is the wind speed and storm surges it will trigger.
Surges of 10 to 15ft are expected in parts of coastal southern Florida and could contribute to life threatening flooding on land. Heavy rain is also forecast and this will exasperate the situation in inland parts of the state.
Unlike Hurricane Harvey which wreaked havoc on Texas last week, Irma is predominantly a wind and surge event, FEMA Chief Brock Long said on Saturday.
Mo the sloth and Kramer the emu are as innocent as they come, but they are doing time in a Florida county jail to protect them from the worst of Hurricane Irma.
So are many horses, pigs, goats, sheep, tropical birds, alligators, snakes, turtles and a few other species that the sheriff's office cares for at a farm for abandoned, abused, confiscated or donated animals.
Once the 426 humans who normally occupy cells at the Monroe County Jail were evacuated by bus to lockups in Palm Beach County, there was an opportunity to move 250 animals indoors, rather than leave them exposed to Hurricane Irma's storm surge, flooding rains and pounding wind.
Five dolphins were moved from the Florida Keys to central Florida in advance of the storm, but most zoos in the Miami area said they were trying to keep their animals in place and secure from whatever Irma will bring.
Authorities in Palm Beach County were being alerted to many animals chained or caged in yards by fleeing owners - these pets have been rescued and will have new homes, they said.
'We are pretty clear, when you surrender your animal you give up your rights,' Dianne Sauve, the director of Palm Beach County Animal Care and Control, told the South Florida Sun Sentinel.
Hundreds of thoroughbreds were moved from low-lying areas of Gulfstream Park, near Miami, to training facilities and barns farther north. Some animal shelters were relocating dogs and cats to safer facilities, and a humane society near Tampa said it needed temporary foster homes for more than 100 dogs.
'We live in a hurricane-prone area so our facilities are designed to accommodate these storms,' said Brian Dowling, the general curator at Lion Country Safari in Palm Beach County, where lions, chimpanzees, rhinos and more were staying put.
Many of their animals were moved into pens designed to hold up even if nearby buildings were lost in storms or tornadoes. Others were kept in their usual day-to-day habitat, some even with gates left open within their normal spaces.
The reason, Mr Dowling said, is simple, animals sense when things are not right, and raising their stress can complicate matters.
SeaWorld Orlando and Busch Gardens Tampa Bay was keeping workers on-site at all hours to care for and monitor the animals.
SeaWorld also took in the five adult male dolphins from Dolphin Discovery in Duck Key, where officials said they will stay 'until they can be safely returned to their home in the Florida Keys'.
Irma provided another reminder of what hurricanes have done to the state's ecosystem. A quarter of a century after Hurricane Andrew, its impact is still seen in the Everglades, where the invasive Burmese pythons decimating populations of native mammals are believed to be descended from exotic snake breeding facilities that were destroyed in the wind.
Most exotic animals that wandered loose in Andrew's wake were recovered, but not the pythons.
With only very large alligators to challenge them, the pythons have thrived in the wetlands. Estimates range from 10,000 to 100,000, but their presence can be seen in the near-total absence of rabbits or other small animals reported by hunters who are now paid by the state to kill the snakes.
In the largest evacuation effort in US history, millions of people in the Sunshine State and in parts of Georgia have been told to leave their home before Irma strikes on Sunday afternoon.
All of southern Florida is under either a hurricane watch or warning and there will be severe weather in more northern parts of the state.
On Saturday, Miami officials warned people who have already fled their homes not to return despite Irma's change in course.
A curfew is in place in the city to deter people from going outside and mandatory evacuation orders are still in place in Miami Dade County and other surrounding areas.
It will last from 7pm until 7am in the City of Miami but others are also being introdcued Mayor Tomás Pedro Regalado told a press conference on Saturday that it was designed to prevent looting which was seen in Hurricane Katrina and Wilma.
All of the airports in southeast Florida are now closed and anyone who is still there is being told to leave urgently or take refuge in one of the shelters being set up.
In Miami, officials admitted they were 'rewriting the book' as they went along to try to prepare for Irma.
Evacuees who have been able to get to a shelter compared the cramped conditions inside to Guantanamo Bay.
Some people are being turned away as high schools and other public spaces reach capacity.
Despite it no longer sitting directly in Irma's path, there were fears Miami could be reduced to a 'third world country' by its winds.
Towering cranes which officials did not have the time to remove before the weekend are at risk of toppling and the windows of the many high-rise apartment buildings will shatter under Category 4 or 5 force sustained winds, storm-chaser Ben McMillan told Fox News.
The monstrous hurricane has already claimed at least 24 lives in the Caribbean and wiped out entire small islands.
Cuba and The Bahamas were battered by the storm on Friday night and Saturday during the day. Irma made landfall on the island nation at around 11.10pm on Friday as a Category 5 hurricane. Its eye hovered over the northwest tip on Saturday.
The winds were ferocious, reaching 160mph in parts of The Bahamas and destroying a wind measuring device in Cuba. The center of Hurricane Irma cleared the Cuban coast Saturday night and entered the Florida Straits, where bathtub-warm water of nearly 90 degrees will enable the storm to intensify.
The outer bands of the hurricane have already reached the U.S., with south Florida and the Keys experiencing increased rain and wind speeds.
The storm was first downgraded from a Category 5 to a Category 4 earlier on Friday morning. But on Friday night, it was again made a Category 5 storm before being relegated back to 4 early this morning.
CNN's Patrick Oppman live tweeted about the terrifying conditions on Friday night. On Saturday, once the storm had downgraded slightly, he went on the air to try to deliver his broadcast.
It gave a frightening picture of the reality on the island which is still largely made up of 1950s architecture and infrastructure.
Oppman struggled to keep his rain coat out of his face and had to retreat into a cupboard of the house where he and his team were filming.
Government officials along with the National Hurricane Center have cautioned that Irma is 'extremely dangerous' with maximum sustained winds of 155 mph. That's strong enough to bring down power poles, uproot trees and rip the roofs off of homes.
The forecasts show expected to track directly up Florida before crossing the state line into Georgia early next week.
Virginia's Gov. Terry McAuliffe has also declared a state of emergency to help the state get ahead of any damage caused by Hurricane Irma.
The declaration also allows Virginia to provide assistance to other states who will be impacted by the storm. Virginia may face possible flooding, high winds and storm surge as a result of Hurricane Irma.
'It is unfortunate that just as our nation has begun the process to repair the catastrophic damage from Hurricane Harvey, that we are faced with another extreme storm,' McAuliffe said on Friday.
'However, if there is one lesson we can take from the tragic events that occurred in Texas, it is that we must redouble our preparation efforts.
A state of emergency allows the commonwealth to mobilize resources, including the Virginia National Guard, and pre-position people and equipment to assist in storm response and recovery efforts.
All Virginians must prepare in advance for the potential impacts of this historic hurricane.
Social workers and police officers gave Miami's estimated 1,100 homeless people a stark choice on Friday: Come willingly to a storm shelter, or be held against their will for a mental health evaluation.
Officials - backed by a psychiatrist and observed by an Associated Press team - rolled through chillingly empty downtown streets as dawn broke over Biscayne Bay, searching for reluctant stragglers sleeping in waterfront parks.
'We're going out and every single homeless person who is unwilling to come off the street, we are likely going to involuntarily Baker Act them,' said Ron Book, chairman of the Miami-Dade Homeless Trust.
Invoking the 'Baker Act' - a law that enables authorities to institutionalize patients who present a danger to themselves or others - is not something law enforcement does lightly, but officers detained at least six people by Friday afternoon. Under the law, they can be held up to 72 hours before the state would have to go to court to prolong their detention.
Book's group was working closely with police, who acknowledged that the effort is unusual: Officials said it is the first time Miami has invoked the law for hurricane preparedness.
About 70 people willingly climbed into white vans and police squad cars Friday, joining others who already arrived at shelters.
About 600 others were thought to remain outside somewhere, exposed to the storm, despite mandatory evacuation orders for more than 660,000 people in areas that include downtown Miami and coastal areas throughout the county.
All Florida's state offices, schools, colleges and universities were ordered to close from Friday until Monday to free up space for evacuation shelters and staging.
The Homeland Security Department is temporarily waiving federal restrictions on foreign ships' transportation of cargo in order to help distribute fuel to states and territories affected by hurricanes Harvey and Irma.
The seven-day waiver specifically affects shipments of refined products, such as gasoline, in hurricane-affected areas.
The Jones Act prohibits such shipments between U.S. points aboard foreign vessels. The last such waiver was in December 2012, for petroleum products delivered after Hurricane Sandy.
Irma poses a bigger menace to power supplies in Florida than Hurricane Harvey did in Texas because Irma is packing near 200 mile-per-hour winds that could down power lines, close nuclear plants and threats to leave millions of homes and businesses in the dark for weeks.
Florida Power & Light's Turkey Point and St. Lucie plants, which can supply power to almost two million homes, are under threat.
The company, a subsidiary of NextEra Energy Inc, is watching the weather and would adjust any plans as necessary.
It can take more than 24 hours to shut down a reactor, so the decision will have to be made well in advance. But bosses are confident the power plants can weather the 185mph storm, as they both have a track record of surviving hurricanes.
The last major hurricane - a storm with winds of at least 111 mph - to hit Florida was Wilma in 2005. Its eye cut through the state's southern third as it packed winds of 120 mph; five people died. Andrew slammed into Florida as a Category 5 storm in 1992 and at the time was the costliest hurricane in U.S. history with damages of $26.5 billion.
With winds that peaked at 185 mph, Irma was the most powerful hurricane ever recorded in the Atlantic.
President Donald Trump said Hurricane Irma 'is a storm of absolutely historic destructive potential' and cautioned people in its path to 'get out of its way' and not worry about possessions.
In a video posted to Facebook, the president urged those in Irma's path to be vigilant and heed the recommendations of all government officials. He said property is replaceable but lives are not, and that safety must come first.
The president and members of his Cabinet bowed their heads in prayer, led by Vice President Mike Pence, as they met at Camp David in Maryland on Saturday afternoon.
The meeting was to discuss federal preparations for Hurricane Irma as the storm prepares to strike Florida.
Trump's exclusive Mar-a-Lago resort in Palm Beach - the unofficial Southern White House - sits in the path of the storm.