Updated at 5:00 a.m. ET Friday
The National Hurricane Center says Irma is now a Category 4 storm. It has maximum sustained winds of 155 mph.
Updated at 11 p.m. ET
Hurricane Irma continued its northwestward sweep Thursday evening, losing little steam as it skirted the Dominican Republic and Haiti and bearing the full force of its 165-mph winds down upon the southeastern Bahamas and away from the Turks and Caicos islands. Forecasters upgraded their alert for South Florida to a warning.
Behind the Category 5 storm is the path of devastation it has already beaten through the eastern Caribbean; ahead of it still, according to the National Hurricane Center, lies the coast of South Florida.
"It has become more likely," the NHC said in its 8 p.m. ET advisory, "that Irma will make landfall in southern Florida as a dangerous major hurricane, and bring life-threatening storm surge and wind impacts to much of the state."
The storm, one of most powerful Atlantic Ocean hurricanes ever recorded, has been blamed for at least eight deaths so far, though there have been reports of several more and the death toll is expected to rise. Hundreds of thousands of other people are being ordered to get out of Irma's way.
A hurricane warning is now in effect for parts of Florida, from Jupiter Inlet (north of West Palm Beach) south around the peninsula to Bonita Beach (south of Fort Myers). A warning means hurricane conditions are expected somewhere within the warning area. The alert also covers the Florida Keys, Lake Okeechobee and Florida Bay.
The National Hurricane Center also highlights a storm surge warning for Jupiter Inlet to Bonita Beach, along with the Keys. The statement says a surge warning means there is a danger of life-threatening inundation from rising water moving inland from the coastline during the next 36 hours.
"Based on what we know now," Gov. Rick Scott said on Thursday afternoon, "Florida will have major hurricane impacts with deadly storm surge and life-threatening winds, and we can expect this all along the eastern coast of Florida."
Still, he said the storm could change its course. For that reason, he added, "every Florida family must prepare to evacuate, regardless of the coast you live on."
Scott ordered all schools, colleges and universities to close and said all state offices would be closed through Monday.
Scott said a storm surge of 5 to 10 feet is expected in several places, though he cautioned that much of the state could feel at least some of Irma's effects, noting that the vast sweep of the storm — extending tropical-storm-force winds up to 185 miles from its center — is currently wider than the Florida Peninsula.
That threat also runs far to the north, according to the NHC: "The chance of direct impacts is increasing in portions of Georgia, South Carolina, and North Carolina, but it is too early to specify the magnitude and location of the impacts."
Leaders in those states aren't waiting to make a move. Gov. Henry McMaster has already declared a state of emergency in South Carolina, while Gov. Nathan Deal has declared a state of emergency in 30 counties in Georgia.
Under the latest forecast models, Irma would swing north and hit Florida full-on as a major hurricane Sunday, moving its way into Georgia by Monday.
Irma's destructive path through the Caribbean
After passing north of Puerto Rico, Irma has followed the same angle past Hispaniola, the island that is home to the Dominican Republic and Haiti. As of 8 p.m. ET, its eye was directly between Haiti and Turks and Caicos.
Irma brought strong winds and flooding to Puerto Rico and the Virgin Islands on Wednesday night, but Puerto Rico was spared the worst of what were then Irma's 185-mph winds.
St. Martin, Anguilla and Barbuda, however, bore the brunt of Irma's destruction.
Daniel Gibbs, president of the Territorial Council of St. Martin, told Radio Caraibes International "95 percent of the territory has been destroyed." That assessment echoed Antigua Prime Minister Gaston Browne, who told CNN that the country's island of Barbuda is now "barely habitable" after Irma's eye hit there early Wednesday.
Things could get worse: On Thursday evening, the NHC upgraded Hurricane Jose, which is now trailing behind Irma, to Category 3 — making it the third major hurricane of the 2017 Atlantic season. A hurricane watch was issued for Antigua and Barbuda and other islands.
In the U.S. Virgin Islands, at least three deaths have been confirmed on St. Thomas, and the White House has declared a major disaster there.
Hospital services on St. Thomas "are now limited to emergency care," the government of the U.S. Virgin Islands said in a statement Thursday afternoon. With both the islands of St. Thomas and St. John without electricity, authorities are struggling to move hospital patients off the islands for treatment, with the help of U.S. military aircraft.
Floodwaters swamped cars and houses in Puerto Rico, where seven rivers are now running above their flood levels, according to the National Weather Service office in San Juan, capital of the U.S. territory.
Cellphone problems and power outages have also hit Puerto Rico, with more than 1 million people — roughly 70 percent of the electricity utility's customers — lacking power because of the storm, local news agencies report.
The human toll and damages from Irma are still being realized, partly because of the wreckage and debris the hurricane has left in its wake and partly because of communications networks being brought down by powerful winds and flying debris.
At least four people were killed and dozens wounded in St. Martin, French officials said Thursday (earlier, Interior Minister Gerard Collomb said eight had died). The island is divided between French and Dutch administrations.
On Barbuda, a toddler died during the storm, Prime Minister Browne told ABS TV/Radio on Thursday.
There are reports of at least two more deaths — one in Anguilla and another in Puerto Rico, where local media relay a police report that an elderly woman died while being moved to a storm shelter. Those deaths have not been confirmed.
The hurricane is now moving west-northwest at 16 mph, progressing toward the Bahamas.
Where Irma goes from here
Irma's path is now projected to pivot north as it nears Florida. The timing of that turn is crucial to millions of people in the state, many of whom live in places already under mandatory evacuation orders. Those orders took effect in Key West on Wednesday; they now also cover barrier islands, including Miami Beach.
Miami-Dade County Mayor Carlos Gimenez's order now covers about 650,000 people, out of the 2.7 million in the county.
Gov. Scott also ordered that all public schools in the state — including K-12 schools and state colleges and universities — close from Friday through Monday. He said the closure will ensure extra space for sheltering evacuees and staging emergency responssefforts.
There has been a run on gasoline, water and batteries, NPR's Greg Allen reports. And while not everyone plans to leave, "the spectacle of what happened to Houston after Harvey, and the memories of Wilma in 2005 and Andrew 25 years ago, in 1992, are really on everyone's minds. I've heard many people talk about Andrew."
In downtown Miami, Greg adds, officials who are preparing for Irma are worried about more than 20 tall construction cranes, especially ones that tower over residential areas.
"They're designed just to withstand winds up to 145 mph," Greg says. "But right now, Irma's winds are far higher ... so a city official warned residents who live nearby those cranes to maybe think about leaving their buildings."
Irma has slightly weakened — its sustained winds have been falling Thursday — but it's likely to remain a Category 5 storm for at least 24 hours, the National Hurricane Center says.
Tropical-storm-force winds will arrive in southern Florida and the Keys on Saturday, the hurricane center predicts.
Those who choose to stay in the Keys will largely have to fend for themselves. The National Weather Service says all Coast Guard search-and-rescue vessels have left the area and the Port of Key West is closing Friday morning.
"This is not a storm you can sit and wait through," Scott warned Floridians on Thursday.
As Irma moves west in the Caribbean, its storm surge poses a dangerous threat. The NHC estimates that by the time the storm has passed, Turks and Caicos and parts of the southeastern and central Bahamas will have seen coastal water rise 15 to 20 feet above normal levels. Cuba's northern coast could get a surge of 5 to 10 feet.
After maintaining 185-mph winds, a tight eye and a well-organized system for more than 24 hours, the powerful storm finally showed a hint of weakness overnight, with the hurricane center saying at 5 a.m. Thursday that Irma had "become a little less organized" with clouds in its eye and a central convection that was "somewhat ragged."
Forecasters are also monitoring Jose, which is tracking behind Irma, as well as Hurricane Katia, which is off Mexico's southern state of Veracruz.
As Jose moves west, it is likely to take a more northward approach than Irma. But before it veers north of Puerto Rico, the hurricane could add to the miseries Irma brought to St. Martin, Barbuda and other areas. Jose is predicted to remain a major hurricane (meaning its winds are at least 111 mph) when it nears those islands early Saturday.
In the Gulf of Mexico, the National Hurricane Center says Katia is heading west-southwest and likely make landfall on Mexico's coast late Friday or early Saturday.