PHOTOS: Irma leaves devastation in its wake as it moves through the Caribbean
Warships and planes were dispatched with food, water and troops after the fearsome Category 5 storm smashed homes, schools and roads, laying waste to some of the world's most beautiful and exclusive tourist destinations.
Hundreds of miles to the west, Florida braced for the onslaught, with forecasters warning that Irma could slam headlong into the Miami metropolitan area of 6 million people, punish the entire length of the state's Atlantic coast and move into Georgia and South Carolina.
PHOTOS: The Path of Hurricane Irma
More than a half-million people in Miami-Dade County were ordered to leave as Irma closed in with winds of 175 mph (281 kph).
"Take it seriously, because this is the real deal," said Maj. Jeremy DeHart, a U.S. Air Force Reserve weather officer who flew through the eye of Irma at 10,000 feet.
The hurricane was still north of the Dominican Republic and Haiti on Thursday evening, sweeping the neighboring nations on Hispaniola island with high winds and rain while battering the Turks and Caico islands on its other side.
Big waves smashed a dozen homes into rubble in the Dominican fishing community of Nagua, but work crews said all the residents had left before the storm. Officials said 11,200 people in all had evacuated vulnerable areas, while 55,000 soldiers had been deployed to help the cleanup.
In Haiti, two people were injured by a falling tree, a national roadway was blocked by debris and roofs were torn from houses along the northern coast but there were no immediate reports of deaths. Officials warned that could change as Irma continued to lash Haiti, where deforested hillsides are prone to devastating mudslides that have wiped out entire neighborhoods of precariously built homes in flood zones.
"We are vulnerable. We don't have any equipment to help the population," Josue Alusma, mayor of the northern city of Port de Paix, said on Radio Zenith FM.
About a million people were without power in Puerto Rico after Irma sideswiped the island overnight, and nearly half the territory's hospitals were relying on generators. No injuries were reported.
The first islands hit by the storm were scenes of terrible destruction.
French Prime Minister Edouard Philippe said four people were confirmed dead and about 50 injured on the French side of St. Martin, an island split between Dutch and French control. The toll could rise because rescue teams had yet to get a complete look at the damage.
At least four people were killed in the U.S. Virgin Islands, and officials said they expected to find more bodies. Authorities described the damage as catastrophic and said crews were struggling to reopen roads and restore power.
Three more deaths were reported on the British island of Anguilla, independent Barbuda and the Dutch side of St. Martin.
Irma also slammed the French island of St. Barts, tearing off roofs and knocking out electricity.
French Interior Minister Gerard Collomb said 100,000 food rations were sent to St. Barts and St. Martin, the equivalent of four days of supplies.
"It's a tragedy. We'll need to rebuild both islands," he said. "Most of the schools have been destroyed."
Photos and video of St. Martin circulating on social media showed major damage to the Philipsburg airport and heavy flooding in the coastal village of Marigot.
Dutch Prime Minister Mark Rutte said the storm "caused wide-scale destruction of infrastructure, houses and businesses."
"There is no power, no gasoline, no running water. Houses are under water, cars are floating through the streets, inhabitants are sitting in the dark in ruined houses and are cut off from the outside world," he said.
In the U.S. Virgin Islands, Gov. Kenneth Mapp said the U.S. military was sending troops to aid relief efforts.
The primary focus for now is "making sure people have meals, water and shelter," Mapp said. "An event of this magnitude is very chilling."
The territory's two islands were battered by 150 mph (241 kph) winds for four hours. Two fire stations, two fire police stations and the hospital on St. Thomas were destroyed. A curfew was ordered for St. John and St. Thomas that also covered about 5,000 tourists who were unable to leave before the storm.
Farther out in the Atlantic, Hurricane Jose strengthened into a Category 3 storm with 120 mph (195 kph) winds and posed a potential threat for Saturday to some of the same islands ravaged by Irma.
Irma, the most potent Atlantic Ocean hurricane ever recorded, appeared increasingly likely to rip into heavily populated South Florida on Sunday afternoon after threatening parts of the Turks and Caicos and the Bahamas on Thursday night and Friday and sweeping along Cuba's northern coast on Saturday.
People in Florida rushed to board up their homes, take their boats out of the water and gas up their cars. With gasoline running out and tensions rising, the Florida Highway Patrol escorted tanker trucks sent to replenish gas stations.
"It is wider than our entire state and could cause major and life-threatening impacts from coast to coast. Regardless of which coast you live on, be prepared to evacuate," Gov. Rick Scott said.
Brian McNoldy, a hurricane researcher at the University of Miami, said Irma could easily prove to be the costliest storm in U.S. history.
French President Emmanuel Macron's office said he would go to the islands as soon as the weather permits it. Saying he was "grief-stricken," Macron called for concerted efforts to tackle global warming to prevent similar natural disasters.
Two Dutch navy ships were in St. Martin with vital supplies. And two Dutch military aircraft were being sent the island of Curacao and on to St. Martin to deliver food and water intended to last the population of 40,000 five days. The aircraft were carrying 100 extra troops to deliver aid, repair infrastructure and restore order.
Britain was sending hundreds of troops and the Royal Navy flagship HMS Ocean to Anguilla, Montserrat and the British Virgin Islands.
In Anguilla, officials reported extensive damage to the airport, hospitals, shelters and schools and said 90 percent of roads were impassable.
On Barbuda, nearly every building was damaged when the hurricane's core crossed almost directly over the island early Wednesday. About 60 percent of its roughly 1,400 residents were left homeless, Antigua and Barbuda Prime Minister Gaston Browne said.
He said roads and telecommunications systems were wrecked and recovery will take months, if not years.
"It is just really a horrendous situation," Browne said.
Chicago woman stranded on cruise ship near Florida as Irma approaches
Tracie Burns of Chicago made a desperate plea on Facebook live. Her cruise ship is still at sea in the Caribbean, unable to dock as Hurricane Irma approaches. Just a few days ago she was all smiles, taking selfies. Now the cruise liner is up against a massive storm.
"I know my family is really worried, but I want you guys to know I'm okay right now," she said in the video.
Burns and her fellow passengers are hoping to dock at Orlando, Fla., Thursday night. But then what?
"My flight doesn't leave until Saturday so I have nowhere to go until then. So I would be stuck in them idle of the hurricane until Saturday," she told ABC7 Eyewitness News.
Flights have already been impacted, and people fleeing Florida are already landing at O'Hare and Midway airports.
"We got out the storm shutters, buttoned up the house, took our important papers with us. And here we go," said Steve Sosnowski.
"I'll take the blizzards here in Chicago anytime, over a hurricane anytime. I'll take that," said Kevin Lofton, who is moving back to Chicago.
Meanwhile, Burns is getting some hometown help from her best friend LaToya Kirk.
"I'm bawling. What do you do? What do you do when your best friend is caught at sea? What do you do?" Kirk asked.
When it's a hurricane, wait it out. But there's no doubt friends are trying.
Traffic nightmare as 500K people told to leave Florida
The race to flee Hurricane Irma became a marathon nightmare for many as more than a half-million people were ordered to leave South Florida on Thursday.
With the storm barreling toward the tip of Florida for perhaps a catastrophic blow this weekend, normally quick trips turned into daylong journeys on crowded highways amid a constant search for gasoline and lodging. Airline seats out of Florida were in short supply as well.
Mari and Neal Michaud loaded their two children and dog into their small sport-utility vehicle and left their home near Cocoa Beach about 10 a.m., bound for an impromptu vacation in Washington, D.C. Using a phone app and calls to search for fuel along the way, they finally arrived at a convenience store that had gasoline nearly five hours later.
The 60-mile trip up Interstate 95 should have taken an hour, said Mari Michaud.
"There was no gas and it's gridlock. People are stranded on the sides of the highway," she said. "It's 92 degrees out and little kids are out on the grass on the side of the road. No one can help them."
The National Hurricane Center issued a hurricane watch for the Keys and parts of South Florida, including some of the Miami metropolitan area of 6 million people. It was the first of perhaps many watches and warnings along the Southeastern coast over the next several days as forecasters warn the storm could hit anywhere from Florida to North Carolina.
As people along the Atlantic coast anxiously watched the behemoth, Irma battered the northern Caribbean, killing at least seven people and leaving thousands homeless after destroying buildings and uprooting trees.
At least 31,000 people fled the Florida Keys, which could begin seeing wind and rain from Irma as early as Friday night, Gov. Rick Scott said. He noted the size of the powerful Category 5 storm, and told residents not to become complacent.
"It is wider than our entire state and could cause major and life-threatening impacts from coast to coast. Regardless of which coast you live on, be prepared to evacuate," Scott said.
NASA secured Kennedy Space Center and SpaceX launched an unmanned rocket for an experimental flight. Kennedy closed its doors to all nonessential staff and a crew of about 120 people will ride out the storm on site.
Most of the critical buildings at Kennedy are designed to withstand gusts of up to 135 mph (220 kph). Irma's wind could exceed that if it reaches Cape Canaveral.
With winds that peaked at 185 mph (300 kph), Irma was the most powerful hurricane ever recorded in the Atlantic.
Georgia Gov. Nathan Deal ordered evacuations for all areas east of Interstate 95, including the city of Savannah, and authorized about 5,000 National Guard members to help with response and recovery.
Noel Marsden said he, his girlfriend, her son and their dog left Pembroke Pines north of Miami with plans to ride out Irma in Savannah, only to find the city was also shutting down because of Irma. Marsden isn't sure where they'll all end up.
"I've got a buddy in Atlanta and a buddy in Charlotte. We'll wind up one of those two places because there are not hotels, I can tell you that," he said.
The last time Georgia was struck by a hurricane of force Category 3 or higher happened in 1898.
Irma's eventual path and Florida's fate depends on when and how sharp the powerful hurricane takes a right turn, National Weather Service Director Louis Uccellini said. The last Category 5 storm to hit Florida was Andrew in 1992. Its winds topped 165 mph (265 kph), killing 65 people and inflicting $26 billion in damage. It was at the time the most expensive natural disaster in U.S. history.
President Donald Trump urged people to "be careful, be safe" during Hurricane Irma. In a tweet, Trump remarked that Irma "is raging but we have great teams of talented and brave people already in place and ready to help."
Trump's exclusive Mar-a-Lago resort in Palm Beach - the unofficial Southern White House - sits in the path of the storm.
U.S. Air Force Reserve weather officer Maj. Jeremy DeHart flew through the eye of Irma at 10,000 feet Wednesday and through Hurricane Harvey just before it hit Texas last month.
DeHart, who has flown into hurricanes about 20 times, said Irma's intensity set it apart from other storms. He's never gone into anything quite so powerful. Or beautiful.
"Spectacular is the word that keeps coming to mind. Pictures don't do it justice. Satellite images can't do it justice," DeHart said.
Passengers fly to Chicago to wait out Hurricane Irma
The last flights out of the Florida Keys will depart later Thursday, before the airport shuts down. Passengers who hoped to escape the coming storm arrived at O'Hare International Airport late Thursday morning.
Kanetha Tenner and her fiance, Terry Beard, were happy to be back home in Chicago after vacationing in Miami.
"It was great until we got the news about the hurricane," Tenner said.
Just filling up to get to the airport was a struggle.
"We waited like 30 minutes in line around the block just to get some gas," Beard said.
Flights into O'Hare were full Thursday morning.
"I planned this trip to move back to Chicago, today, two months ago. Just so happens, Hurricane Irma was in effect. Everyone was like, 'Whoa, you got out of there just in time,'" said Kevin Lofton, a passenger.
Maria Derchi arrived in Chicago with her husband and two dogs. They'll be staying with her sister.
"The storm looks pretty scary. I lived though Andrew," Derchi said of the hurricane that hit the Bahamas and Florida in 1992.
Some people bought one-way tickets. Alec Schade plans to wait to see what Irma will do.
"I made it a one-way ticket, that way I can either go back Monday, if it's better, or in three weeks, if I have to," Schade said.
Jim Strykowski, a former Chicagoan who now lives in Florida, said he prefers the Windy City's weather to hurricanes.
"(1967) was the massive snowstorm when I was shoveling snow off my dad's house when I was a senior in high school. Snow storms, I can handle," Strykowski said.
Flights to Miami were still departing for Miami late Thursday morning. American Airlines will shut down operations in Miami this weekend because of Irma.
WLS-TV contributed to this report.