Over 2.5 million Americans in the southeasternmost US state are under evacuation orders or warnings as Ian threatens to bring a deadly storm to some areas.
Residents of Florida's Gulf Coast have boarded up their homes, packed up their vehicles and headed for higher ground as Hurricane Ian drew near, threatening to bring a deadly storm surge and more than a foot of rain to some areas.
On Tuesday, more than 2.5 million Floridians were under evacuation orders or warnings with the sprawling storm on track to make landfall as a Category 3 hurricane on Wednesday evening somewhere along the Gulf Coast.
A Category 3 storm carries maximum sustained winds of up to 208 km per hour. The latest 5 pm hurricane advisory put Ian's top winds over 190 kph.
Ian was most likely to come ashore south of Tampa near Sarasota, the National Hurricane Center said.
That region is home to sandy beaches and scores of resort hotels, a favourite with retirees and vacationers alike.
'Time to evacuate is now'
DeSantis warned of the potential for devastating Hurricane Harvey-like flooding that struck the Houston area in 2017, the result of a slow-moving storm piling up high water.
Parts of central Florida could see as much as 0.6 metres of rain from Ian, according to the National Weather Service.
Florida's director of emergency management, Kevin Guthrie, urged residents in evacuation zones to move to safety.
"The time to evacuate is now. Get on the road," he said.
To ease evacuations, authorities suspended toll collections along major highways in Central Florida, the Tampa Bay area and the interstate stretch across the Everglades known as Alligator Alley.
If Ian strikes Tampa, it would be the first hurricane to make landfall in the area since the Tarpon Springs storm in 1921.
It also may prove to be one of the costliest as the latest simulations show the estimated cost from storm damage and other impacts ranging from $38 billion to more than $60 billion, Enki Research said on Tuesday.
Closings, power outages
Nearly 60 Florida school districts were either closed on Tuesday or planned to be closed by Wednesday, DeSantis said. Officials planned to use many of the schools as shelters during the storm and its aftermath.
Commercial airlines cancelled more than 2,000 US flights due to the storm.
The St Petersburg-Clearwater International Airport, located on a vulnerable peninsula east of Tampa Bay, ceased operations at 1 pm on Tuesday, and the Tampa International Airport will shut down at 5 pm.
The Orlando International Airport has no plans to close but officials say they are monitoring the storm.
Tampa Electric warned customers to be prepared for "extended outages." The company will institute a "targeted interruption" of service to a part of downtown Tampa on the western edge of the city.
The Walt Disney Co announced it was closing its Florida theme and water parks on Wednesday and Thursday while the National Football League's Tampa Bay Buccaneers relocated to Miami, where they will practice this week ahead of their game against the Kansas City Chiefs on Sunday.