Poverty is one of the main reasons people choose not to evacuate, Trump said.
"Some of the areas are very poor," he said. "It's not easy for a person without the necessary money to leave."
FEMA Administrator Brock Long said federal resources are already in place throughout the affected areas. He added that FEMA teams, equipment and personnel have been deployed across the state and are ready to assist.
The hurricane, a category 4 storm, was forecast to make landfall early Wednesday afternoon. Earlier, Florida Gov. Rick Scott advised those who hadn't already evacuated that it was now too late.
"First responders will not be able to come out in the middle of the storm," he tweeted. "If you chose to stay in an evacuation zone, you must seek refuge immediately."
He declared a State of Emergency for the Florida Panhandle and Big Bend regions, where storm surge could reach 13 feet.
"That means the water will come miles in-shore," Scott said. "Listen to local officials. We can rebuild your house but we cannot rebuild your life."
In addition to storm surge, hurricane force winds are expected to cause widespread power outages. Electrical line crews from across the country are heading for Florida ahead of the storm so they are in position to restore power after the storm passes.
More than 200 utility workers gathered at the Pensacola Interstate Fairgrounds Tuesday from as far away as Michigan. Combined with Gulf Power's employees and contractors, there are more than 19,000 crews ready to go, Scott said.
Millions of Floridians lose power a year ago when Hurricane Irma affected the entire state. Some were without electricity for more than a week. Scott said there have been no fuel shortages or outages, yet.
Major airlines canceled all flights at Northwest Florida Beaches International Airport, but the facility said it will resume normal operations Thursday.
In Panama City, the Hathaway Bridge closed after winds surpassed 50 mph. Residents in that city were encouraged to shelter in place.
Engineering plans are also underway to get bridges and highways re-opened as soon as possible.
Michael will be the fourth storm rated Category 3 or higher to hit the Florida Panhandle since 1950. There are more 3.7 million people under a hurricane warning in Florida.