Mandatory evacuation orders came into effect for 120,000 people in Panama City Beach and across other low-lying parts of the coast.
The Florida Governor has said the state is "100 per cent ready" to face the might of Michael. It is expected to weaken as it moves up into the southeastern United States.
Long said several hospitals in the Panhandle were hit by the hurricane and patients had to be evacuated.
It appeared to be so powerful that it remained a hurricane as it moved into south Georgia early Thursday.
Mark Wallheiser via Getty Images People line up for gasoline outside Tallahassee, Florida, on Monday as Hurricane Michael bears down on the northern Gulf coast.
The U.S. Coast Guard in Mobile, Alabama, says its crews have rescued 27 people, mostly from damaged homes.
An Associated Press team drove for miles and encountered extensive destruction around Panama City. "We need to be ready for this", NHC Director Ken Graham said in an update Tuesday morning, urging people in the storm's path to finish preparations and evacuate if they're in an emergency area. They're also trying to figure out the extent of damage to roads and bridges.
State offices, schools and universities were to close on Tuesday through the end of the week in panhandle counties.
Based on its internal barometric pressure, Michael was the third most powerful hurricane to hit the USA mainland, behind the unnamed Labour Day storm of 1935 and Camille in 1969.
Floridians in counties where election offices closed Tuesday for Hurricane Michael will be able to register to vote the day those offices reopen.
He said strong winds picked up a portable carport Wednesday and dropped it down on the roof.
Damage in Panama City near where Michael came ashore Wednesday afternoon was so extensive that broken and uprooted trees and downed power lines lay almost everywhere. But he said the sheriff told him it looked like a bomb had gone off.
Hurricane Michael’s eye isn’t targeting Manatee County. But it will affect our weather | Bradenton Herald
Hurricane Michael made landfall on Wednesday afternoon as a category four storm with 155mph (250km/h) winds in the state's Panhandle region. The storm's maximum sustained winds have decreased to 50 miles per hour (80 kph) and it was moving to the northeast at 21 miles per hour (33 kph).
Hurricane Michael swiftly intensified into a Category 2 over warm Gulf of Mexico waters Tuesday amid fears it would strike Florida on Wednesday as a major hurricane.
Similar scenes are emerging across the Florida Panhandle, where Hurricane Michael left more than 350,000 without power and entire neighborhoods in ruins after hitting Wednesday afternoon near Mexico Beach as a risky Category 4 storm.
A reporter and photojournalist from the Tampa Bay Times ventured there in the dark early Thursday, finding the town of about 1,000 nearly impassable. It also set off transformer explosions and knocked out power to more than 388,000 homes and businesses.
Each line is a different forecast model projection for the track of Michael later this week.
Scarcely 72 hours after its formation, this late-season tropical system has achieved major hurricane status as it bears down on the coast of Florida.
- Power outages: More than 780,000 customers in Georgia, Florida, Alabama and SC without power. Data from a NOAA Hurricane Hunter aircraft indicate that maximum sustained winds have increased to near 125 miles per hour (205 km/h) with higher gusts. Forecasters said it would unleash damaging wind and rain all the way into the Carolinas, which are still recovering from Hurricane Florence's epic flooding.
After being battered for almost three hours by strong winds and heavy rains, roads in Panama City were virtually impassable and trees, satellite dishes and traffic lights lay in the streets.
The most powerful hurricane on record to hit Florida's Panhandle left wide destruction and wasn't almost finished Thursday as it crossed Georgia toward the Carolinas, still reeling from epic flooding in Hurricane Florence.
Wakulla County issued a dire warning, saying it won't open any of its shelters - because they're safety-rated only for storms up to Category 2 strength, WFSU reports.
The storm has already killed a man in Florida and a girl in Georgia.