Florida-bound Hurricane Irma strengthens back to a Category 5 as it makes landfall in Cuba

Hurricane Irma strengthened back into a Category 5 storm Friday night as it made landfall on the Camaguey Archipelago of Cuba with maximum sustained winds of 160 mph, according to the National Hurricane Center.

Irma's status as a Category 4 storm was relatively short-lived, having been downgraded from a Category 5 storm early Friday morning.

As of 2 a.m. ET, Irma was about 275 miles south-southeast of Miami and moving about 12 mph toward the west, the National Hurricane Center said.

Hurricane Irma remains forecast to hit the Florida Keys as a Category 5 storm.

South Florida is already experiencing power outages, according to the Florida Power & Light Company. As of 3 a.m. Saturday, in Miami-Dade County there were 9,613 outages affecting 1,124,252 customers. In Broward County, which includes Fort Lauderdale, there were 456 outages affecting 939,339 customers.

Ahead of Irma's arrival in the Sunshine State, the last flights departed Friday night from Miami International Airport and Fort Lauderdale-Hollywood International Airport. Miami's airport officially remains open, while Fort Lauderdale's airport is closed on Saturday and Sunday.

Also ahead of its arrival, The Associated Press reported late Friday night that many ATM machines across southwest Florida were out of cash as people stocked up in case Hurricane Irma power outages make credit card transactions impossible.

Meteorologists expect Irma to make landfall in the Keys between 5 a.m. and 7 a.m. ET on Sunday. Overnight projections of Irma's path showed less of a threat to the Carolinas as the monster storm appeared likely to move directly up the middle of Florida and curve inland.

The National Weather Service's Key West office issued a dire warning in the wake of the updated forecast.

"Obviously Hurricane Irma continues to be a threat that is going to devastate the United States," Brock Long, administrator of the Federal Emergency Management Agency (FEMA), said at a press conference Friday morning. "We're going to have a couple rough days."

The National Hurricane Center on Friday cautioned that Irma is "extremely dangerous," with maximum sustained winds of 155 mph, which are strong enough to uproot trees, bring down power poles and rip off the roofs and some exterior walls of well-built frame homes.

Hurricane and storm surge warnings for Florida as of early Friday, Sept. 8, 2017. (ABC NEWS)

The National Hurricane Center issued its first hurricane warnings for Florida overnight, warning residents that "preparations to protect life should be rushed to completion."

Mandatory evacuation orders have been issued for barrier islands, coastal communities, low-lying areas and mobile homes across Florida, including the counties of Brevard, Broward, Collier, Indian River, Martin, Miami-Dade, Monroe, Palm Beach and St. John. According to the Florida Division of Emergency Management, 5.6 million Floridians have been told to evacuate.

Southern Florida is likely to receive 6 to 10 inches of rain and up to 20 inches locally from Hurricane Irma. (ABC NEWS)

Meteorologists predict Irma will continue to weaken as the storm moves inland Sunday into Monday. Irma will approach Jacksonville on Monday around 8 a.m. ET with winds of about 75 mph, which would make it a dangerous Category 1 hurricane. Then, Irma should weaken rapidly to a tropical storm, depression or a remnant low later Monday as it moves across state lines into Georgia, then potentially Alabama and Tennessee on Tuesday into Wednesday, meteorologists say.