The Category 4 storm is packing maximum sustained winds of 150 miles per hour as it nears the coastline near Panama City Beach.
Storm surge could reach up to 14ft in parts of the hurricane zone.
Hurricane Michael made landfall in Mexico Beach, Florida on Wednesday afternoon, as thousands took refugee in local shelters.
Forecasters are predicting 4 to 6 inches of rain with locally higher amounts, but wind continues to be the primary concern for weather and emergency officials.
Meteorologists have predicted storm surges of up to 14 feet in Apalachicola, with windspeeds of 140mph already reported in the Gulf.
"Michael is likely to produce potentially catastrophic wind damage where the core of the hurricane moves onshore in the FloridaPanhandle, and everyone in the hurricane warning area should prepare for life-threatening hurricane winds".
Tropical Storm Leslie could once again redevelop into a hurricane as it spins in the open Atlantic.
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.
With the storm approaching ever closer, Gov. Scott warned that first responders will no longer be able to make it to evacuation zones.
An Extreme Wind Warning was issued for Hurricane Michael's eyewall about 11:45 a.m. Wednesday. There is no way to hide from storm surge.
More than 300 miles of coastline was under threat, the National Weather Service has said.
Forecasters said some regions of the United States may see 30cm of rain, and storm surges of up to 3.6m. The forecast for the Onslow County area is less with about two to three inches of rain, mainly on Thursday but some rain from the storm to begin Wednesday.
"Everybody's hunkered down, we're watching for debris", he said.