All the way up to the Carolinas, destructive flooding from the storm's rains is expected.
Florida officials said Michael, packing winds of 155 miles per hour (250 kph), was the most powerful storm to hit the southern U.S. state in more than a century.
As the Category 4 storm's center crossed nearby, Mulligan said, the concrete building shook and vibrated against sustained winds around 155 miles per hour.
The wind and storm surge related insurance industry loss from hurricane Michael is estimated to be between $2 billion and $4.5 billion by Corelogic, based on a pre-landfall data assessment of the storms impacts to insured assets. A risky storm surge continued along the coastal Florida panhandle; a National Ocean Service station in Apalachicola was reporting 5 feet of water above the ground level.More news: International Monetary Fund raises Japan growth forecast, cuts global estimate due to trade tension
Without the warm waters of the Gulf of Mexico to provide it fuel, forecasters say Michael will be downgraded even further to a tropical storm by Thursday morning.
By late Wednesday, the storm had moved toward Georgia.
Briefing President Donald Trump at the White House, Federal Emergency Management Agency (FEMA) chief Brock Long said Michael was the most intense hurricane to strike the Florida Panhandle since 1851. The debris was a problem in many coastal communities and still hundreds of thousands of people were also left without power.
That is rarefied air: only three storms have hit the U.S.at Category 5: an unnamed storm that devastated the Florida Keys in 1935; Camille, which hit MS in 1969; and Andrew, which plowed across South Florida in 1992.
Meanwhile, tropical storm warnings were in effect for parts of Alabama, Florida, Georgia, South Carolina and North Carolina.More news: McConnell to AP: "'Nobody's going to beat" Murkowski
Across the bay in Panama City Beach, a resort city on the Gulf of Mexico known for its white-sand beach and amusement parks, winds of about 100 miles per hour furiously whipped the trees in the early afternoon and pulled apart homes.
General Terrence O'Shaughnessy, commander of North American Aerospace Defense Command, said some Florida residents may have been surprised by the rapid growth of the storm.
"We haven't seen her since the tree hit the den". It was a relatively calm year except for hurricanes Michael and Florence last month.
-Strorm riders: Roughly 375,000 people in Florida warned to evacuate; many refused. He has covered hurricanes in the state for decades.
Bo Patterson, the mayor of Port St. Joe, just south of Mexico Beach, rode out the storm in his house seven blocks from the beach, describing the scene outside as "very, very scary". "This happened so quickly", he said.More news: Princess Eugenie and Jack Brooksbank's wedding: How to watch in Canada
The National Hurricane Center (NHC) said Michael would dump as much as 8 inches of rain in some areas. Neighborhood streets flooded as waves battered the shoreline. Homes were swallowed in storm surge.