Local relief groups at the ready to assist after Hurricane Irma. (WJZ)

Half a million Floridians began to flee the coast Thursday ahead of the state's gravest hurricane threat in a generation.

South Florida was under a hurricane watch, with the outer bands of Hurricane Irma's life-threatening winds and storm surge expected to arrive by daybreak Saturday. Georgia was also on guard as meteorologists worked to refine a forecast that could also include a hit to the Southeastern coast.


Irma, which had maintained Category 5 strength for a record 66 hours as of Thursday evening, is not expected to weaken before reaching the mainland United States. It had winds of 175 mph as it closed in on Turks and Caicos and the Bahamas, and was expected to remain a Category 4 or 5 storm for days, surrounded by warm waters. By 11 p.m. winds reduced to 165 mph.

Hurricane and storm surge warnings were issued for parts of Florida, including Jupiter Inlet southward around the Florida peninsula to Bonita Beach, as well as for the Florida Keys.

Meteorologists urged South Florida residents to make preparations for the massive storm by Friday night.

"It is wider than our entire state and could cause major and life-threatening impacts from coast to coast," Florida Gov. Rick Scott said. "Regardless of which coast you live on, be prepared to evacuate."

The National Hurricane Center meanwhile warned of chances that the storm could strike Georgia or the Carolinas after tearing through the Sunshine State. Some forecasting models suggested that Irma could hit the Southeastern coast Monday or Tuesday, potentially as a major storm with winds greater than 111 mph.

Long-term forecasts suggest the storm will eventually move inland toward the Ohio Valley, bringing rainy, windy weather to Maryland around Tuesday.

But while forecasters at the weather service's Baltimore/Washington office said any impact from the storm would not compare to conditions in the Caribbean, they cautioned that flooding, damaging winds and tornadoes could still be possible here.

Gov. Larry Hogan urged Marylanders to prepare for some impact, "while we have the benefit of time."

As many as half a million people were ordered to leave their homes in South Florida on Thursday, causing gridlock on northbound highways. Irma could be the first Category 5 hurricane to hit Florida since Andrew in 1992, which had 165 mph winds and killed 65 people.

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 that that city was also shutting down because of the storm. Marsden wasn't sure where they'll 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.

After Hurricane Harvey, which devastated southeastern Texas last month, Irma could be just the second major hurricane to make landfall in the U.S. since Wilma — which also struck Florida — in 2005.

Images of water rescues and submerged homes across Houston were prompting many to take Irma's threat more seriously than they might otherwise. Jenna Wulf, a native Floridian who is six months pregnant, said that considering what Harvey did, she stocked up on water and was closing hurricane shutters on her home in suburban Plantation.


"I think it's such devastation that you'd be silly not to go through the motions," she said.

The first islands hit by Irma were scenes of terrible destruction Thursday.

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.

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 three people were killed in the U.S. Virgin Islands, officials said. They described the damage as catastrophic, saying crews were struggling to reopen roads.

The British island of Anguilla, independent Barbuda and the Dutch side of St. Martin together accounted for three more reported deaths.

About a million people were without power in Puerto Rico after Irma sideswiped the island Wednesday night, but there were no immediate reports of large-scale casualties.


The severity and direction of Irma's wrath on the U.S. mainland will depend on where the storm makes an expected right turn toward the north. Hurricane center forecasters said the timing of the turn remains "filled with uncertainty."

If the hurricane veers right soon enough, it could rake the Bahamas but avoid a direct strike on Florida. It could turn later and go up the Gulf coast or it could buzz right up the South Florida coast, putting millions of people in the path of a once-in-a-generation hurricane.

Still, at roughly 400 miles wide, the hurricane is virtually certain to affect South Florida, whether through a few days of rainy, windy weather, a direct hit or something in between. Hurricane-force winds extend 50 miles from the center and tropical-force winds extend 185 miles from the center.

"The odds are definitely looking worse for the east coast of Florida, given the latest set of model runs," said Jeff Masters, meteorology director for the website Weather Underground, who used to fly on NOAA Hurricane Hunters. "It's unusual to have the top four models all give the same track in advance, and they're all doing that now."

Two other hurricanes spinning in the Atlantic basin are not forecast to affect the United States. Jose, which became a major hurricane Thursday afternoon in the middle of the Atlantic, could brush the northern Caribbean but — at least for now — is expected to turn out to sea before making any landfall. Katia, the other storm, is expected to hit Mexico's Gulf Coast late Friday.

Philip Klotzbach, a hurricane researcher at Colorado State University, said it was only the fourth time on record there have simultaneously been three hurricanes, two of which are major storms, in the Atlantic.

The Associated Press contributed to this article.

Hurricane and tropical storm tracker for Hurricane Irma and Hurricane Jose

The latest locations and forecasts for hurricanes and tropical storms to keep track of Hurricane Irma and Hurricane Jose.