Hurricane Irma, which was downgraded to a Category 3 storm on Saturday, is set to gain its second wind before buffeting the outskirts of Florida's coast early Sunday morning with "catastrophic and life-threatening" conditions, the National Weather Service reported.
As of 5pm Eastern, the destructive weather system was located about 115 miles south of Key West, where Florida officials have already issued mandatory evacuation orders that have sent millions of residents fleeing for safety.
Irma will likely make landfall as a Category 4 storm. The NWS stated that "major hurricane force winds" were expected to batter the area at daybreak, with winds speeds well over 100 miles per hour making their way up the state's western coast.
On Friday, the agency warned via Twitter that "nowhere in the Florida Keys will be safe," and that residents should clear out while they were able.
Since Irma passed over Cuba, weather conditions across Florida have been deteriorating progressively, and officials have upgraded warnings across areas considered most at risk. Irma's westward shift has now put major Floridian cities such as Naples and Tampa at risk. Irma has already killed dozens across the Caribbean, leaving decimation in its wake.
Powerful storm surges are currently in the forecast for Florida's Gulf Coast, even as swaths of South Florida — most notably Miami, Fort Lauderdale and Palm Beach County — are seen in less jeopardy than they were just a day ago. Still, the storm's toll is expected to be high, even as Congress hastily approved $15 billion in emergency spending in preparation for Irma's arrival.
The Tampa area has not taken a direct hit from a major hurricane in nearly a century.
"You need to leave — not tonight, not in an hour, right now," Gov. Rick Scott warned residents in the evacuation zones ahead of the storm's predicted arrival on Sunday morning. Separately, FEMA's top official issued a stark warning for residents who chose to defy evacuation orders: They'd be left to their own devices, with no immediate help.
"You're on your own until we can actually get in there, and it's safe for our teams to support local and state efforts," Brock Long told CNN. "The message has been clear -- the Keys are going to be impacted, there is no safe area within the Keys, and you put your life in your own hands by not evacuating."
For days, the forecast had made it look as if the Miami metropolitan area of 6 million people on Florida's Atlantic coast could get hit head-on with the catastrophic and long-dreaded Big One.
The westward swing in the hurricane's projected path overnight caught many on Florida's Gulf coast off guard. By late morning, few businesses in St. Petersburg and its barrier islands had put plywood or hurricane shutters on their windows, and some locals groused about the change in the forecast.
Since Irma began cutting a swath across the Atlantic Ocean, nearly 10,000 flights have been cancelled at airports in the storm's path. Nearly 7,000 of them have been in and out of airports in Florida, according to data from FlightAware.
--The Associated Press contributed to this article.