Over 2.5 million people were told to evacuate as the southern U.S. state of Florida braced for Hurricane Ian, which gathered enough strength to near a Category 5 storm, before making landfall Wednesday.

As Ian Lashed the state's southern tip with tropical storm-force winds, Florida residents emptied grocery shelves, boarded up windows and fled to evacuation shelters.

Ian, which pummeled Cuba earlier Tuesday and left the entire Caribbean island nation without power, was expected to crash ashore into Florida on Wednesday evening south of Tampa Bay somewhere between Sarasota and Naples as a potentially deadly Category 4 hurricane.

A Category 4 storm on the five-step Saffir-Simpson scale carries steady winds of up to 209 kph (130 mph). The first hurricane advisory on Wednesday put Ian's maximum sustained winds near 195 kph, ranking it a Category 3, but said the storm was expected to strengthen.

The National Hurricane Center (NHC) in Miami warned that Ian would also unleash pounding surf, life-threatening coastal flooding and more than a foot of rain in some areas, as authorities urged more than 2.5 million residents to evacuate their homes for higher ground.

By late Tuesday night, tropical storm-force winds generated by Ian extended through the Florida Keys island chain to the southernmost shores of the state's Gulf Coast, according to the hurricane center.

The NHC also issued storm surge warnings for much of western Florida's shoreline, predicting coastal flooding of up to 12 feet from wind-driven high surf.

"The time to evacuate is now. Get on the road," Florida's director of emergency management, Kevin Guthrie, said during a news briefing on Tuesday evening, urging residents to heed evacuation warnings.

Governor Ron DeSantis warned late Tuesday night that evacuation would become difficult for those who waited much longer to flee because increasing winds would soon force authorities to close highway bridges.

Urgency & complacency

"You need to get to higher ground, you need to get to structures that are safe," DeSantis said, adding that widespread power outages would leave millions without electricity once the storm strikes.

U.S. Federal Emergency Management Agency chief Deanne Criswell said she worried that too few Florida residents were taking the threat seriously.

"I do have concerns about complacency," Criswell said on Tuesday. "We’re talking about impacts in a part of Florida that hasn’t seen a major direct impact in nearly 100 years. There’s also parts of Florida where there’s a lot of new residents."

If Ian strikes the Tampa area, it would be the first hurricane to make landfall there since the 1921 Tarpon Springs storm.

It also may prove one of the costliest, with data modeling service Enki Research projecting storm-related damages ranging from $38 billion to more than $60 billion.

Ian moved across the southeastern edge of the Gulf of Mexico headed for Florida after thrashing Cuba earlier on Tuesday, knocking out the country's electrical grid and ravaging the western end of the island with violent winds and flooding.

The Florida coastal zone at highest risk for U.S. landfall is home to miles of sandy beaches, scores of resort hotels and numerous mobile home parks, a favorite with retirees and vacationers alike.

"We're right on the water, along a canal, so ... this could be devastating," Melissa Wolcott Martino, 78, a retired magazine editor in St. Petersburg, said as she and her husband loaded valuables and pets into their car for a drive to their son's home north of Tampa on Tuesday.

To ease traffic congestion during evacuations, authorities suspended toll collections along major highways in central Florida and Tampa Bay area.

Some residents, such as Vanessa Vazquez, 50, a software engineer in St. Petersburg, said they planned to ride out the storm at home despite evacuation warnings.

"I'm staying put," Vazquez said. "I have four cats and I don't want to stress them out. And we have a strong house."

Schools to shelters

Nearly 60 Florida school districts had canceled classes due to the hurricane, DeSantis said. More than 175 evacuation centers were opened statewide, the governor said, many of them school buildings converted to shelters.

"This is a mobile home community, and they really need this shelter," said Fabiola Galvan Leon, a preschool teacher acting as a bilingual translator for hundreds of evacuees who flocked to Reddick Elementary School in Wimauma, Florida, southeast of Tampa.

Commercial airlines reported more than 2,000 storm-related U.S. flight cancellations, with the St. Petersburg-Clearwater International Airport and Tampa International Airport shut down on Tuesday.

The shelves at a nearby Walmart store had been stripped almost bare, though a contingent of shoppers wandered the aisles, hurriedly grabbing the last remaining boxes of water, canned goods and loaves of bread.

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.

The storm's approach also disrupted the Gulf Coast energy industry, as personnel were evacuated from 14 production platforms and rigs, shutting down about 11% of the region's oil output.