Michael has been designated a Hurricane, the U.S. National Hurricane Center said Monday.
With maximum sustained winds of 120 kilometers per hour, the National Hurricane Center said that Michael was expected to worsen.
Hurricane conditions are expected across the far western part of the Cuban province of Pinar del Rio later Monday, where a hurricane warning is in effect.
The center said Michael will move northward across the Yucatan Channel later Monday, and across the eastern Gulf of Mexico Monday evening through Wednesday.
Meanwhile, tropical storm conditions are expected across the remainder of the warning areas in Cuba and the Yucatan Peninsula later Monday.
The center warned Michael's rains could produce life-threatening flash floods and mudslides in Cuba's mountainous terrain.
Michael is expected to move inland over the Florida Panhandle or Florida Big Bend area on Wednesday and then move northeastward across the southeastern United States Wednesday night and Thursday.
The center warned that heavy rainfall from Michael could result in "life-threatening flash flooding" in the Florida panhandle and has advised all residents to heed the advice of local officials.
Rick Scott, governor of the U.S. southern state of Florida, has declared a state of emergency for 26 counties, a move that frees up resources for storm preparation.
"This storm will be life-threatening and extremely dangerous," Scott said Sunday.