The National Weather Service in Tallahassee issued its first-ever extreme wind warning just as the storm was about to make landfall.
Overnight, the system exploded in strength, becoming a Category 4 storm.
Hundreds of thousands of local residents fled as the hurricane approached, but many stayed behind, not realizing they would be facing what has been called an "unprecedented" storm.
As the storm approached Florida Panhandle, powerful winds snapped trees in half, while storm surge pushed water well beyond the beaches and into homes and businesses.
Video posted online showed the roof of a hotel in Panama City Beach, — just 20 miles from where the storm made landfall — being ripped off amid the strong gusts.
Officials warned that loose items, like patio furniture, could easily become deadly projectiles, and urged people to stay indoors.
"If you are in a coastal area, do not leave your house…. If you made the choice not to evacuate, please find a place to shelter," Florida Gov. Rick Scott said Wednesday.