Washington: Michael has strengthened to an "extremely dangerous" Category Four hurricane as it rumbles toward the Gulf Coast of Florida, the National Hurricane Centre said Wednesday.
It said the storm is now packing maximum wind gusts of 210 kilometres, could grow even more and is expected to make landfall later in the day along the Florida Panhandle or Big Bend area as a "life-threatening event".
A storm surge of up to four metres is expected in some areas, the centre said.
Separately, the National Weather Service in the state capital Tallahassee issued a dramatic appeal for people to comply with evacuation orders.
"Hurricane Michael is an unprecedented event and cannot be compared to any of our previous events. Do not risk your life, leave NOW if you were told to do so," it said.