If it makes landfall, Matthew would be the first major hurricane — Category 3 or higher — to hit the U.S. mainland since Wilma in 2005.
Regardless of whether it's a direct hit, Scott said the impact on Florida "will be catastrophic."
Tropical storm systems typically diminish as they interact with land, but Matthew has stubbornly refused to weaken significantly — not when it slammed first into Haiti, and only slightly when it passed over a sparsely populated area of Cuba.
That's because Atlantic hurricanes usually veer out to sea, thanks to low pressure over the ocean in late summer and early autumn. But the National Weather Service said high pressure has persisted over the western Atlantic and the East Coast in the recent days — trapping Matthew close to the coast and the warm waters of the Caribbean.
South Carolina officials said Wednesday evening that more than 250,000 people had been evacuated from Charleston and other coastal areas — packing westbound traffic on Interstate 26 as motorists headed west, where they found gas hard to get, stores sold out of essential supplies and hotels at capacity.
One man got so frustrated by the traffic that he fired shots at Moncks Corner police officers in Berkeley County, S.C., Wednesday afternoon, the county sheriff's office said.
Lucas Felkel, 35, died Wednesday evening at Trident Medical Center after a deputy returned fire and shot him, the sheriff's office said. No officers or deputies were injured.
Two men were also reported injured in Broward County, Florida, in accidents as they tried to reinforce their homes.
A 56-year-old Weston man suffered non-life-threatening injuries when his aluminum shutters fell on him Wednesday morning, said Mike Jachles, a spokesman for the Broward County Sheriff's Office.
And another man was airlifted to Broward Health Medical Center with undisclosed injuries after he fell 20 feet from a ladder while putting up shutters Wednesday night at his home in the Weston subdivision of Savannah, Jachles said.