Some additional strengthening is possible before landfall, which is expected Wednesday afternoon, before weakening as it crosses across the southeastern U.S. Maximum sustained winds have increased to 145 miles per hour.
"We are catching some hell", said Timothy Thomas, who rode out the storm with his wife in their second-floor apartment in Panama City Beach.
There was a storm surge warning in effect from the Okaloosa/Walton county line to the Anclote River in Florida, and a storm surge watch in effect from Ocracoke Inlet, N.C., to Duck, N.C. According to the US Energy Information Administration. It strengthened from a tropical storm on Sunday to a Category 1 hurricane with 75-mph winds on Monday.
A man in Greensboro, Florida, was also killed when a tree crashed through his home and trapped him.
The state Division of Emergency Management reported 388,100 power outages just after 6 p.m., without any breakdown.
Warm water is like jet fuel for hurricanes, and a combination of balmy conditions in the Gulf of Mexico, a lack of disturbance from wind shear and rapid intensification near the coast turned Michael into a historic storm, according to hurricane experts.
In St. Marks, John Hargan and his family gathered up their pets and moved to a raised building constructed to withstand a Category 5 after water from the St. Marks River began surrounding their home.
Meanwhile, Michael continues its track across southern Georgia toward the Carolinas.
The Carolinas are still recovering from Hurricane Florence, which left dozens dead and is estimated to have caused billions of dollars in damage last month.
National Hurricane Center Meteorologist Dennis Feltgen said: "We are in new territory".
Mexico Beach is a small tourist town toward the center of Florida's panhandle.
Hurricane Michael, now officially the third-most powerful storm in U.S. history, ripped tree roots out from the ground and tore off roofs as it came ashore.
So it will take some time for the full scale of the property damage from hurricane Michael to be understood. The only other hurricane that landed with comparable force this late in the year was Hurricane Hazel in 1954, but Michael was much stronger when it came ashore, Mr. Henson said.
Meteorologists use another measure to evaluate hurricane intensity: central pressure.
Looking at the entire hurricane season, Michael had the strongest winds since 1992 and Hurricane Andrew. Hurricanes form over the Atlantic and North Pacific oceans and cause most damage to the Americas while typhoons form in the Northwest Pacific Ocean, impacting Asia.
For insurance-linked security (ILS) and catastrophe bond interests though, this initial estimate perhaps will give some comfort that the impacts to the sector will not be particularly significant, compared to a similarly severe storm impacting an area of Florida with higher levels of property density and exposure. The storm has 100 miles per hour winds.