Winds of tropical storm force will be felt in the area starting early Wednesday, and mandatory or voluntary evacuation orders already have been issued in at least 22 counties on the Florida Gulf Coast head of the storm.
At 2 p.m. Tuesday, the National Hurricane Center said Michael had top sustained winds of 110 miles per hour (175 kph). The Florida Panhandle, southeast Alabama, and southern Georgia will see 4 to 8 inches of rain, with isolated areas facing up to 12 inches, the National Hurricane Center said.
The storm's rapid intensification over the past two days, despite shifting winds, "defies traditional logic", according to hurricane forecasters.
Most gas stations in downtown Tallahassee are out of gas as Hurricane Michael approaches. "We can rebuild your house, but we cannot rebuild your life".
Hurricane Michael will influence South Florida's weather for the rest of the week, but the effects are not expected to be significant, forecasters say.
Nadine, which is no threat to land, is notable as the 14th named storm this hurricane season, which was forecast to have less activity than during a normal year.
Florida Governor Rick Scott, who has suspended his Senate campaign due to the impending storm, warns that this hurricane is "going to be historic" and cause more destruction than the state's panhandle has seen in decades.
With the rainfall, the potential for gusty winds of about 15 miles per hour to 40 miles per hour depending on proximity to the Michael's outer bands. The storm's center is expected to move inland over the Florida Panhandle or Florida Big Bend area before moving northeastward across the Southeastern U.S.
Hurricane Michael grew into a major Category 3 storm as it howled closer to Florida's Gulf shore on Tuesday, sending tens of thousands of coastal residents fleeing to higher ground one day before its expected arrival with towering waves and roof-shredding winds.More news: Hurricane Michael European Model Shows Storm Intensifying
Duke's service area includes parts of the state expected to be hit hard Wednesday by Hurricane Michael, including part of Bay County and the coastal counties of Gulf, Franklin and Wakulla.
The 11 a.m. advisory for Hurricane Michael shows it is up to a 110-mph Category 2 hurricane - one mile below a Category 3.
"You can not hide from storm surge, so. get out if an evacuation is ordered", he said.
Even as the storm churned some 200 miles away from the Tampa Bay area, its effects could still be felt Tuesday as floodwaters reached the low-lying streets in areas such as Clearwater Beach and St. Pete Beach. Cedar Key to Crystal River could see storm surges topping 6-8 feet.
"I know people are tired from Florence, but don't let this storm catch you with your guard down", North Carolina Gov. Roy Cooper said, adding, "A number of homes have rooftop tarps that could be damaged or blown away with this wind".
In neighbouring Alabama, Governor Kay Ivey declared an emergency for the entire state on Monday in anticipation of wind damage, heavy rains and power outages.
In Florida, nearly three dozen shelters opened or were prepared to open as the storm neared. The storm is set to slam into the Florida Panhandle on Wednesday.
Scott also said Monday afternoon that state health officials are reaching out to hospitals and nursing homes to be prepared.
By late Tuesday, Michael was causing major disruptions to US oil and gas production as it churned north, gathering greater strength over the warm waters of the Gulf of Mexico. Harris and Troup counties north of Columbus are not part of the state of emergency. "The state is not taking this storm lightly and neither should any family".