ABC News(MIAMI) — Hurricane Irma skirted north of the Dominican Republic early Thursday as the powerful Category 5 storm set its sights on south Florida after leaving a trail of death and destruction in the Caribbean. At least 13 people have been killed.

Irma, dubbed the most powerful Atlantic storm in a decade, had maximum sustained winds of 180 mph early Thursday morning as it moved away from the northern coast of Puerto Rico and over the Dominican Republic and Haiti. The wind speeds were down slightly from the day before, but only by 5 mph, according to the National Weather Service.

“Some fluctuations in intensity are likely during the next day or two, but Irma is forecast to remain a powerful Category 4 or 5 hurricane during the next couple of days,” the National Weather Service said in its advisory.

As of 8 a.m., Irma was about 110 miles north of Punta Cana in the Dominican Republic, and moving west-northwest as it raced toward Turks and Caicos. The storm is expected to pound the Turks and Caicos archipelago southeast of the Bahamas in the evening. Storm surge could be up to 5 feet high on the northern coast of the Dominican Republic and up to 20 feet on Turks and Caicos.

Much of Turks and Caicos and the Bahamas could get 8 to 12 inches of rain, with as much as 20 inches in isolated spots through Saturday, according to the National Weather Service.

Millions of children in Haiti and the Dominican Republic are at risk, according to Save the Children organization.

“Deadly storms have a bias against children. Storms often leave a lasting impact on young minds. Relief efforts should prioritize children — their needs, their emotional well-being,” Unni Krishnan, director of Save the Children’s emergency health unit, said in a statement Thursday.

The National Weather Service projects Irma will be near the central Bahamas by Friday and then make landfall in south Florida, near Miami, on Sunday morning as a Category 4 hurricane, bringing high winds, abundant rainfall and potentially dangerous storm surge.

Florida Gov. Rick Scott, who declared a statewide emergency earlier this week, has warned that the “massive storm” could be more treacherous than Hurricane Andrew, which devastated the Sunshine State 25 years ago.

“I want everybody to understand the importance of this. This is bigger than Andrew,” Scott said Wednesday in an interview from Tallahassee with ABC News’ Good Morning America co-anchor Robin Roberts. “This could be worse.”

At a press conference Thursday morning, Scott said Irma could bring “life-threatening” damage to Florida, and he urged residents on the state’s east and west coasts to be prepared to evacuate.

Mandatory evacuations have been delivered in two Florida counties: Monroe County and Miami-Dade County’s Zones A and B. Monroe covers the Florida Keys, while Miami-Dade’s Zones A and B include Miami Beach and Key Biscayne. The state has also issued voluntary evacuations in Broward and Collier counties. Scott said late Wednesday that he expects additional orders will be given once the storm grows closer.

Miami-Dade County Mayor Carlos Giménez told ABC News that about 150,000 people have been ordered to evacuate so far. But up to 400,000 people in Miami-Dade County, the southeastern-most county on the U.S. mainland with more than 2.7 million residents, could be ordered to evacuate on Thursday, he said.

Hurricane warnings were in effect all the way to the western Bahamas on Thursday; however, there are no hurricane warnings yet for Florida.

Irma leaves 13 dead in the Caribbean

The islands of St. Martin and Barbuda were especially hard hit in the storm on Wednesday, and officials there are continuing to assess the damage.

Irma delivered massive destruction to St. Martin, and at least eight people were killed and 21 more injured on the small island, according to French Interior Minister Gérard Collomb.

Although the airport was not destroyed, it is also not functional, and support will have to be delivered via helicopter, Collomb said. He noted that 100,000 military emergency rations will be sent to the population.

One person was also killed in Barbuda on Wednesday. The island suffered near-total destruction, with 90 percent of its structures destroyed, according to Antigua and Barbuda Prime Minister Gaston Browne.

“I have to admit that I am now the bearer of bad news, in that I journeyed to Barbuda this afternoon and what I saw was heart-wrenching — I mean, absolutely devastating,” Browne told state-owned ABS Television Radio on Wednesday. “In fact, I believe that on a per capita basis, the extent of the destruction in Barbuda is unprecedented.”

Barbuda recorded the strongest winds of any island in the path of Irma, with 155 mph gusts measured Wednesday morning. Meanwhile, the U.S. Virgin Islands saw a wind gust of 131 mph on Buck Island north of St. Croix.

One person also died in Anguilla where Irma caused “moderate to severe damage” to “critical infrastructure,” including the hospital, airport, fire station, police station, government buildings, public utilities and roads, according to the Department of Disaster Management in the British territory.

Although Puerto Rico largely avoided the worst of Irma, with the highest wind gust on the Caribbean island measured at 70 mph, at least three people died there as a result of the storm’s impact, according to the governor’s office. A 79-old woman died at the hospital after she fell while being transported to a shelter, another woman died of electrocution, and a man died in the hospital after getting in a car accident while driving in poor weather conditions.

Puerto Rico Gov. Ricardo Rossello said at a press conference Thursday morning that 6,200 people had hunkered down at shelters while Irma dropped 2 to 8 inches of rain across the island and up to 12 inches of rain in some isolated spots. One million customers were without power, and 17 percent of the U.S. territory doesn’t have access to safe water.

Officials began assessing the extent of the damage Thursday, Rossello said.

Meanwhile, the U.S. Coast Guard on Thursday launched crews to conduct search-and-rescue flights in Puerto Rico and the U.S. Virgin Islands to assist anyone potentially in distress after Irma, while also conducting overflight and surface port assessments.

“Our first priority is ensuring safety of lives and helping anyone in distress. Following that, reopening the ports is a top priority, but we have to make sure we also do it safely,” Capt. Eric King, commander of Sector San Juan and the incident commander, said in a statement. “Opening the port prematurely could create a situation for a greater risk or incident, which could ultimately result in an even longer port closure. We must ensure the port is clear of any obstructions and any significant damage to the port infrastructure from the storm that would prevent the flow of commercial commerce.”

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