The National Hurricane Center (NHC) announced Monday that the tropical storm had nearly reached hurricane strength and could even be at or near major hurricane strength by Tuesday night, when it is expected to approach northwestern Florida.
Life-threatening storm surge warnings have been issued for these areas, as well.
Florida State University said its campuses in Tallahassee and Panama City will be closed from Tuesday to Friday.
Michael was packing sustained winds of up to 85 miles per hour (140 kph) and gaining strength as it skirted past Cuba's western tip en route to a likely Wednesday landfall as the most powerful storm to strike the Florida Panhandle in at least a decade.More news: XXXTentacion's Mother Accepts His Award for Favorite Soul/R&B Album at AMAs
The National Hurricane Center (NHC) said the storm could unleash coastal storm surges of up to 3.7 meters along the Florida Panhandle and dump up to 30 cm of rain across Florida, Georgia and SC.
The first rains from Michael were already beginning to soak the Florida Keys on Monday, with up to four inches (10 centimeters) expected to fall through Tuesday.
Florida governor Rick Scott said Hurricane Michael is a "monstrous storm" that has the potential to be devastating to the Florida Panhandle.
While it's likely to weaken as it moves across the southeastern United States, its heavy rains and flooding effects will spread far and wide.
In Pender County, officials are encouraging residents and businesses that suffered roof damage from Hurricane Florence to secure structures with tarps ahead of the storm.More news: Storm Michael could soon form, hit USA midweek
"On the state level, we are prepared", said Ivey.
Michael is no longer a tropical storm.
The chances of tropical storm winds are low but it is possible that strong gusts Tuesday night into Wednesday might reach tropical storm force.
Hurricane warnings are in effect from the Alabama/Florida state line to the Suwanee River along Florida's Big Bend.
While the NWS says Hurricane Michael will make landfall in Florida as a "major hurricane", it also predicts it will weaken as it moves through the Southeast on Wednesday night and Thursday. The governor warned people who live in the Big Bend and Florida Panhandle to prepare for flooding and high winds.More news: Wozniacki wins 30th title with China Open victory
Michael brought heavy rainfall and hurricane-force winds to western Cuba on Monday, with its center brushing close to the island as the storm headed into the Gulf of Mexico. Residents are being urged to evacuate inland.