The storm was forecast to move through the southeastern United States on Wednesday and Thursday, passing through Georgia and the Carolinas, which are still recovering from Hurricane Florence last month.
An Air Force Reserve Hurricane Hunter crew reported top sustained winds up to of 145 miles per hour with higher gusts.
Michael battered the shoreline with sideways rain, powerful gusts and crashing waves, swamping streets and docks, flattening trees, stripped away leaves, shredding awnings and peeling away shingles.
In Mexico Beach, with a population of 1,000, the storm shattered homes, leaving floating piles of lumber.
Those winds were tearing some buildings apart in Panama City Beach.
"If you and your family made it through the storm safely, the worst thing you could do now is act foolishly", he said.
"Water will come miles in shore and could easily rise over the roofs of houses", he said. He said people will "not be dragged out of their homes", but anyone who stays behind will be on their own once the storm hits.
After daylight Thursday residents of north Florida would just be beginning to take stock of the enormity of the disaster.
Hurricane-force winds extend outward up to 45 miles (75 km) from the center and tropical-storm-force winds extend outward up to 175 miles (280 km).
Smith, in Gadsden County, said the situation was unsafe even for emergency personnel.
Diane Farris, 57, and her son walked to a high school-turned-shelter near their home in Panama City to find about 1,100 people crammed into a space meant for about half as many.
Olivia Smith, public information officer for the Gadsden County Board of County Commissioners, said there was "one hurricane-related fatality", adding that the incident was "debris-related".
In the Florida Panhandle and surrounding areas, people are frantically boarding up homes, filling sandbags and planning for evacuation routes away from the storm's projected strike zone. Promptly follow evacuation and other instructions from local officials.
Rick Reichmuth, Fox News' chief meteorologist said Michael was the fourth most powerful storm to ever make landfall in the U.S.in terms of wind, and the third most powerful in terms of pressure, at 919 mb. By 8am on Tuesday (1am Wednesday NZT), top winds had reached 155kmh, and it was forecast to strengthen into a "major" Category 3 hurricane with maximum sustained winds of more than 179kmh.
Based on wind speed, it was the fourth-strongest, behind the Labour Day storm (184 mph), Camille and Andrew in 1992.
Tens of thousands of people have been ordered to evacuate in Wakulla, Gulf and Bay counties.
The National Weather Service calls for highs in the upper 80s for the rest of the week, with lows in the 70s.
Where has Hurricane Michael hit so far? "Do not risk your life, leave NOW if you were told to do so", it said.
A hurricane warning is now posted for the Florida Gulf coast from the Alabama/Florida border to Suwanee River, Florida, including Pensacola, Panama City and Tallahassee. "This happened so quickly", he said.
Trump issued an emergency declaration for Florida, freeing up federal funds for relief operations and providing the assistance of FEMA, which has more than 3,000 people on the ground.
The governors of North and SC urged residents to brace for more heavy rain and storm-force winds as Michael plows northward up the Atlantic seaboard.