The storm will bring an 8-12 foot storm surge.
Forecasters say the storm will gain more intensity through Tuesday, with a chance it will weaken somewhat as it nears land in Florida.
CNN reports that such language is warranted, for Michael is now "slashing Cuba" and is expected to reach Category 3 status (with sustained winds from 111-129 mph) by Wednesday when it reaches the USA mainland.
Early Tuesday, Michael's top sustained winds had risen some to 90 miles per hour (144 kph) as it headed north at 12 miles per hour (19 kph).
Michael is expected to sweep up the East Coast, and tropical storm-force winds were projected to reach the state Thursday, according to the center's projections.
The hurricane's current wind speeds are 120km/h.
On the beach, expect Monday's high risk of rip currents on Atlantic beaches to continue into midweek and a raised risk for beaches on the Gulf of Mexico side starting Tuesday.
With the ground saturated from Hurricane Florence, inland flooding is also predicted.
"You can't survive storm surge", he said.
Florida Governor Rick Scott declared a state of emergency for 35 counties, activating 1,250 National Guard troops in preparation for the storm. The NWS also warned of life-threatening winds along the Florida Gulf Coast. In the days following Hurricane Irma past year, 14 people died after a South Florida nursing home lost power and air conditioning.
Of the elderly and infirm patients, Scott had a blunt message for their caregivers: "If you're responsible for a patient, you're responsible for the patient. Take care of them", he said.
"We have never seen a storm like this in this part of our state", he said after the briefing. Southern Maryland and the Eastern Shore are expected to see the most rain - 2 to 5 inches are possible, he said.
Tens of thousands of people have been ordered to evacuate in Wakulla, Gulf and Bay counties, Reuters reported.
High winds weren't the only danger.
"Heavy rainfall from Michael could produce life-threatening flash flooding from the Florida Panhandle and Big Bend region into portions of the Carolinas through Thursday", the hurricane center said.
Three Florida Panhandle counties have issued mandatory evacuation orders ahead of Hurricane Michael's expected landfall. Forecasters also warned spinoff tornadoes would also be a threat.
The city of Tallahassee has opened two locations for residents to pick up sandbags in anticipation of flooding. The city of Pensacola tweeted to residents, "Be sure you have your emergency plan in place". Local authorities fear power outages and major tree damage from Michael.