Hurricane Michael was upgraded to a Category 4 storm Wednesday ahead of its landfall and could cause "potentially catastrophic" damage to the state of Florida’s panhandle, according to the National Hurricane Center (NHC).

The storm is expected to make landfall later Wednesday with forecasters estimating it may get stronger as it nears land due fueled by the Gulf of Mexico's warm waters.

Michael was just 90 miles southwest of Panama City, Florida, early Wednesday, moving at 13 mph (21 kph) with sustained winds currently reaching 145 mph (233 kph).

The outer bands have begun to hit the coast with tropical storm level winds.

"The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline," the NHC said.

Officials are expecting up to 10 inches (25 centimeters) of rain, with some areas receiving 12 inches (30 centimeters).

The NHC warned life-threatening storm surges could devastate the panhandle, with some areas potentially getting a 13-foot (4-meter) surge.

Florida Governor Rick Scott declared a state of emergency in 35 counties and received approval from U.S. President Donald Trump for a pre-landfall emergency declaration that will provide Florida with assistance and resources from the Federal Emergency Management Agency.

"Families under mandatory evacuation in the Panhandle and Big Bend need to move inland RIGHT NOW. The decisions you & your family make over the coming hours could be the difference between life & death," Scott tweeted.

Michael will be the first major hurricane to hit Florida in October since 2005 and is one of the most dangerous storms to strike the panhandle in recent decades.