The National Hurricane Center issued a hurricane warning and a storm surge warning late Thursday for south Florida and the Florida Keys as the storm headed toward the state.
Irma was located 585 miles east-southeast of Miami as of late Thursday, the National Hurricane Center said. The storm's fercious winds had slowed a bit to a still-powerful 165 miles per hour.
The eye of Irma is expected to move westward from the Turks and Caicos Islands and toward the southeastern Bahamas overnight Thursday.
A hurricane warning is in effect for Jupiter Inlet southward around the Florida peninsula to Bonita Beach; Florida Keys; Lake Okeechobee; Florida Bay; Haiti from the northern border with the Dominican Republic to Le Mole St. Nicholas; southeastern Bahamas; the Turks and Caicos Islands; Cuban provinces of Camaguey, Ciego de Avila, Sancti Spiritus, and Villa Clara; Central Bahamas and Northwestern Bahamas.
A storm surge warning is in effect for Jupiter Inlet southward around the Florida peninsula to Bonita Beach and the Florida Keys.
French, British and Dutch rescuers rushed aid to a heavily damaged string of Caribbean islands Thursday after Hurricane Irma, a powerful Category 5 storm, left a path of destruction.
Irma left at least 10 people dead, scores injured and thousands homeless as it spun toward Florida for what could be a catastrophic blow this weekend.
Warships and military 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.
Meanwhile, Florida braced for the onslaught, with forecasters warning 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.
More than a half-million people in Miami-Dade County were ordered to leave.
"Take it seriously," said Maj. Jeremy DeHart, a U.S. Air Force Reserve weather officer who flew through the eye of Irma at 10,000 feet. "Because this is the real deal."
The U.S. National Hurricane Center's (NHC) 8 p.m. advisory said Irma is pummeling the Turks and Caicos island, has sustained winds of 175 mph and the storm is moving west-northwest at 16 mph.
NHC says in the latest advisory that the government of the Dominican Republic has discontinued the hurricane warning east of Cabo Frances Viejo and the tropical storm warning for the southern coast of the Dominican Republic.
The NHC predicted Irma would remain at Category 4 or 5 as it passed just to the north of the Dominican Republic and Haiti, neared the Turks & Caicos and parts of the Bahamas by Thursday night and skirted Cuba on Friday night into Saturday.
The Associated Press contributed to this report.