A strengthening Hurricane Matthew steamed toward Florida with winds of 140 mph Thursday as hundreds of thousands of people across the Southeast boarded up their homes and fled inland to escape the most powerful storm to threaten the Atlantic coast in more than a decade.

In Florida, Gov. Rick Scott said the state, its skies already darkening from the deadly storm’s outer bands of rain, could be facing its “biggest evacuation ever.”

The hurricane picked up steam as it closed in, growing from a Category 3 to a Category 4 storm by late morning.

It barreled over the Bahamas and was expected to scrape nearly the entire length of Florida’s Atlantic coast beginning Thursday evening. From there, forecasters said, it could push its way just off the coasts of Georgia and South Carolina before veering off to sea.

About 2 million people in Florida, Georgia and South Carolina were warned to head inland.

As people hurried for higher ground, authorities in South Carolina said a motorist died on Wednesday after being shot by deputies during a dispute along an evacuation route.

Matthew killed at least 29 people in the Caribbean as it sliced through Haiti, Cuba and the Bahamas. Twenty-three of those deaths were in Haiti, where the full extent of the death and destruction was still unknown.

As of 11 a.m. EDT, Matthew was 180 miles southeast of West Palm Beach and moving toward the city at about 14 mph. Nearly all of Florida’s Atlantic coast and Georgia’s entire coast were under hurricane warnings.

Forecasters said the storm could dump up to 15 inches of rain in some spots and cause a storm surge of 5 feet to 8 feet.

“This is a dangerous storm,” Scott warned. “The storm has already killed people. We should expect the same impact in Florida.”

Patients were transferred from two Florida waterfront hospitals and a nursing home near Daytona Beach to safer locations.

Major theme parks in inland Orlando remained open, but Walt Disney World and Universal Studios canceled Halloween events Thursday night.

The Fort Lauderdale Airport closed to all flights late in the morning.

Deborah Whyte walked her dogs at Jupiter Beach Park in the morning to check the surf.

“We boarded up our house and I boarded up my store” in Tequesta. “And we’re just hunkering down and waiting for it,” she said.

But others as far off as Georgia and South Carolina rushed to leave.

On Tybee Island, home to Georgia’s largest public beach, Loren Kook loaded up his pickup truck with suitcases and a computer late Wednesday afternoon to hit the road to metro Atlanta.

“It seems like a lot of the longtime residents are staying,” said Kook, who moved to the coast four years ago. “I’ve never sat through a Category Whatever. I’ll watch it on TV.”

Georgia Gov. Nathan Deal urged more than a half-million residents to leave their homes, the first evacuation seen in coastal Georgia in 17 years.

(AP)