Hurricane Irma hit Cuba's north coast "hard" early Saturday, the National Hurricane Center said, as Florida's governor warned of an "unbelievable" storm surge as high as 12 feet.
The deadly storm weakened slightly to a Category 4 hurricane overnight, with maximum sustained winds of 130 mph, and was about 225 miles south of Miami at 8 a.m. ET, the center said in an update.
It is expected to reach the Florida Keys Sunday morning.
Irma weakened as it passed over terrain in Cuba but the NHC said it was likely to restrengthen as it crossed relatively warm waters on its path to Florida.
It is forecast to travel along Florida’s west coast but the size of the system means hurricane-force winds will extend all the way to the east coast, National Hurricane Center Acting Director Edward Rappaport said on MSNBC Friday.
"So while the trend to the west might be a little better for the east coast, it's actually much worse now for the Florida Keys and the west coast," he said. "They could see the most extreme of the winds and the storm surge."
About 5.6 million people in Florida — more than one quarter of the state's population — were ordered to evacuate and another 540,000 were told to leave the Georgia coast.
Florida Gov. Rick Scott warned Saturday that time was running out for people in evacuation zones on Florida's west coast to get to safety.
"It's getting late ... if you're not on the road on the west coast by noon you need to get to a shelter...get off the road," he said on NBC's TODAY.
Scott said his biggest worry was rising water from the "unbelievable storm surge" that could be as high as 12 feet. "You're not going to survive it. If you're in an evacuation zone you've got to get out and you've got to get out now," he said.
But he added that the State of Florida was prepared. "We're resilient, we're strong, we're going to help each other and we're going to get through this," he said.
President Donald Trump in a video message Friday warned "this is a storm of absolutely historic destructive potential." He urged everyone in its path to heed evacuation orders.
Florida Power & Light, the nation's third-largest electric utility, warned it was expecting "unprecedented" power outages. FPL CEO Eric Silagy said power outages could affect about 9 million people.
The hurricane killed at least 23 people as it raked through the Caribbean earlier this week. The storm was a Category 5 with 160 mph winds late Friday, slightly faster than earlier Friday when it was a Category 4.
On Cuba, thousands of tourists were evacuated from low-lying keys off the coast dotted with all-inclusive resorts ahead of the storm's approach. All residents of the area were under mandatory evacuation orders from the Cuban government, which was moving tens of thousands of people from vulnerable coastline.
The hurricane ravaged small islands in the northeast Caribbean, including Barbuda, St. Martin and the British and U.S. Virgin Islands, ripping down trees and flattening homes and hospitals.
Rappaport said late Friday that the hurricane's maximum sustained winds might come down if it stays over land for several hours, but the danger posed to Florida will not change.
"It won't change that the hurricane force winds extend out 75 miles from the center, it won't change that you're going to have a storm surge that's life threatening," he said. The Keys could see a storm surge of 5 to 10 feet, with waves on top.
The typically bustling downtowns of Miami, Fort Lauderdale and Naples were near empty Friday. Residents had either evacuated or were making last-minute preparations, resigned to sitting through the Category 5 Hurricane in their homes and hoping for the best.
Tony Marcellus struggled to figure out how to get his elderly mother and grandfather from their home near the ocean in West Palm Beach to his place in Atlanta, 600 miles away. Flights and rental cars were sold out, so he hired an Uber driver to take them 170 miles to meet him in Orlando.
Manny Zuniga left his home in Miami at midnight Thursday and it still took him and his family 12 hours to get 230 miles to Orlando — a trip that normally takes four hours.
"We're getting out of this state," he said, filling up the gas tank of his tightly-packed SUV in Orlando. His final destination is a relative in Arkansas.
"Irma is going to take all of Florida," he added.
At least 900 flights were canceled in Florida as of Friday afternoon. Miami International Airport saw 75 percent of its schedule scrubbed. It will remain open but no flights are expected to arrive or depart on Saturday or Sunday.
Gas supplies were put under strain. According to GasBuddy, 38 percent of gas stations in Miami/Fort Lauderdale are out of fuel and 55 percent of Gainesville stations were depleted. In response to the shortages, Scott directed Florida Highway Patrol to escort resupply trucks to gas stations.
There are currently 1,700 members of Florida Highway Patrol working the roadways on 12-hour shifts, Scott said.
The U.S. Navy on Friday ordered an aircraft carrier and two other ships to head to get underway to be in position to provide humanitarian and search assistance if necessary. A fourth ship conducting local operations was ordered to join the group, the Navy said.
Georgia was also preparing for the hurricane effects of Irma. Gov. Nathan Deal announced mandatory evacuations to go into effect Saturday at 8 a.m. ET for certain low-lying parts in the state's south.
Even as forecasts showed the storm's center could enter Georgia far inland, Deal urged nearly 540,000 coastal residents to flee, noting Irma's path remains unpredictable. Forecasts show it could enter the state Monday anywhere from the Atlantic coast to the Alabama state line.
Meanwhile Hurricane Jose shadowed Irma's movements, strengthening to a Category 4 storm on Friday with walloping winds of 150 mph, according to the National Hurricane Center. Jose has brought another hurricane watch to Antigua, Barbuda and Anguilla, and St. Martin only two days after the islands in the region were damaged by Irma.
Kalhan Rosenblatt reported from Naples. Erik Ortiz and Elizabeth Chuck reported from New York.