Hurricane Irma is winding its way up to the mainland United States, having devastated Caribbean islands like Barbuda and St Maarten over the last few days. Irma's since been downgraded to a Category 4 hurricane, but that still means it's bringing 150 mph winds and heavy rain, and South Florida is bracing for the worst.

Right now, Irma is on its way toward Cuba and the Bahamas, and the US National Hurricane Center says it could make landfall in Florida on Saturday night. "Severe hurricane conditions are expected over portions of the Florida peninsula and the Florida Keys beginning late Saturday," the National Hurricane Center said last night. “Irma could make landfall in southern Florida as a dangerous major hurricane, and bring life-threatening storm surge and wind impacts to much of the state." The storm is then expected to make landfall near heavily-populated Miami on Sunday, and then approach Orlando on Monday, though it may weaken to a tropical storm later that day.

FEMA administrator Brock Long warned today that Irma could potentially destroy large swaths of the southeastern coast. "I can guarantee you that I don’t know anybody in Florida who’s ever experienced what’s about to hit South Florida," he said, urging residents from Alabama to North Carolina to begin preparing for Irma's arrival. "We're going to have a couple rough days," he said. The Weather Channel predicts Irma will bring "life-threatening storm-surge inundation north and east of the hurricane's path."

So far, officials in Florida have issued mandatory evacuation orders for barrier islands, coastal communities, low-lying areas and mobile homes statewide, with evacuation counties including Brevard, Broward, Collier, Indian River, Martin, Miami-Dade, Monroe, Palm Beach and St. John's.

Thousands of South Floridians are fleeing the region, clogging up Interstates 95 and 75 and the Florida Turnpike in what CNN said could become "one of the largest evacuations in US history." Gas stations have been running out of fuel in the exodus, prompting the Florida Highway Patrol to employ fuel tankers to resupply stations.

Georgians and residents of the Carolinas are also bracing for the storm—it is possible Irma will make landfall near the Georgia/South Carolina coast, or even move north through Florida into Southern Georgia. Either way, the region will likely be subject to storm surges, high winds, and even flooding. "Even if Irma’s winds weaken and its Saffir-Simpson category drops, Irma could still be capable of extreme storm surge, depending on its track and the geography of its landfall location(s)," Jeff Masters, a meteorologist with wunderground.com, told the Weather Channel.

And right behind Irma is Hurricane Jose, which has since grown to Category 4 and is heading for the Caribbean.