The governors of South Carolina and Georgia ordered at least 1 million people to evacuate their coasts beginning Monday after Hurricane Dorian left devastation in the northwest Bahamas and headed for the U.S. East Coast.

South Carolina Gov. Henry McMaster and Georgia Gov. Brian Kemp both announced mandatory evacuation orders to take effect at noon Monday in advance of the slow-moving, Category 5 hurricane.

The South Carolina order covers all of Beaufort and Charleston counties and parts of the rest of the state's coastal counties, which state officials estimated covered 830,000 people.

The Georgia order covers people who live east of Interstate 95 in the counties along the Atlantic coast; that includes Savannah and most of its 150,000 residents, as well as more than 50,000 in coastal communities like Brunswick, St. Marys and Richmond Hill. Naval Submarine Base Kings Bay, in Camden County, told its 15,000 military and civilian personnel and their families to expect an announcement soon.

South Carolina Gov. Henry McMaster acknowledged the difficulty in moving so many people out of the area at one time, but said he couldn't risk undertaking the evacuations in stages. The state Public Safety and Transportation departments said they would reverse the direction of traffic along evacuation routes to ease the flow.

"We know we can't make everybody happy, but we believe we can keep everyone alive," McMaster said. 

Kemp announced his evacuation orders in a statement late Sunday.

Dorian was forecast to have a long life, remaining a hurricane for the next five days. Hurricane watches and warnings were already in effect Sunday afternoon for parts of the Florida coast, where the storm was expected to move "dangerously close" beginning Monday night or Tuesday, forecasters said.

A hurricane warning was issued for Jupiter Inlet to the Volusia-Brevard county line in Florida, while a hurricane watch was issued from the Volusia-Brevard line to the Georgia line. Forecasters said Dorian was expected to arrive along the Georgia and South Carolina coasts sometime midweek.

"We are preparing for the worst, but we are praying for the best," said Elliott Summey, chairman of the Charleston County, South Carolina, Council.

North Carolina, meanwhile, also "has to take this storm seriously," Gov. Roy Cooper said Sunday. "Be ready. It might be far away, but it is already kicking up rip tides at our coast."

Dorian made landfall Sunday afternoon with estimated sustained surface winds of 185 mph and gusts reaching 220 mph at Elbow Cay, Abacos, in the northern Bahamas. The power of the storm was second only to that of Hurricane Allen in 1980, with its 190 mph winds.

"It is not very often that we measure such strong winds," the hurricane center said.

Twelve to 24 inches of rain, and up to 30 inches in some areas, were expected in the northwestern Bahamas, which could lead to life-threatening flash floods, the center said. The Tourism Ministry said only certain parts of the northwestern Bahamas had conducted evacuation procedures, and it strongly advised visitors to leave.

Steven Strouss, a meteorologist for NBC News, said that since records began in the 1850s, the Abaco Islands and Grand Bahama Island had never before been directly hit by a Category 5 storm.

Dorian was east of Freeport on Grand Bahama Island and moving west at just 6 mph early Monday. It was expected to continue inching westward to west-northwest for the next day or two. Forecasters said it would then likely gradually turn northwest, meaning the core of the storm "will continue to pound Great Abaco this evening and move near or over Grand Bahama Island tonight and Monday."

Bahamanian authorities said Sunday night that they had lost contact with the Abaco Islands because of an island-wide power failure that knocked out most telephone service. And they said they feared Grand Bahama Island could be hit even harder.

"The path of Dorian across Abaco is a short distance," Health Minister Duane Sands said on ZNS Bahamas radio.

Grand Bahama, by contrast, "is laid out lengthwise across the width of Dorian," Sands said. "Now, Grand Bahama is in for a number of days. ...

"We don't know what we're going to find," he said. "The expectation is there will be catastrophic consequences on both Abaco and Grand Bahama."

Strouss, the NBC News meteorologist, cautioned that even though Dorian might not make landfall along Florida's east coast, it would track very close, with torrential and flooding rainfall, tropical storm-force winds, dangerous storm surges and life-threatening rip currents.

"The hurricane will spin close enough to lash the Southeast United States Monday through Wednesday as it churns northward up the coast," Strouss said, adding that the storm could cause major travel disruptions.

Miami International and Fort Lauderdale/Hollywood International airports were still open Sunday night. The Fort Lauderdale airport said it would close at noon Monday, while the Miami airport said it would suspend operations as soon as winds reached 55 mph.

Mandatory evacuation orders were issued beginning Sunday night or Monday for mobile homes and low-lying and flood-prone areas from Palm Beach County north to the Daytona Beach area.

Marge Dombrowski, who has lived in Palm Beach County, Florida, for more than 60 years, said Sunday that she and her family were planning to leave on Monday morning.

"What you're going to find when you come back — we never know," Dombrowski said in an interview. "It's all up to Mother Nature. I just pray, pray that the man upstairs will look down on us and protect us."

Also among those evacuating were 400 animals from the South Florida Wildlife Center in Fort Lauderdale, such as hawks, burrowing owls, Eastern screech owls, a black vulture, a red-bellied woodpecker, a gopher tortoise and a flock of black-bellied whistling ducklings.

President Donald Trump, who called off his planned trip to Poland over the weekend to oversee the response to Dorian, said he would discuss possible evacuations Sunday in a scheduled meeting with officials of the Federal Emergency Management Agency, or FEMA.

"It seems to be one of the biggest hurricanes we've ever seen. And that's the problem," Trump told reporters on Sunday. "We don't know where it is going to hit, but we have an idea."

During a news conference with FEMA officials on Sunday, Trump said he was unsure whether he had ever heard of a Category 5 hurricane's forming.

"I knew it existed, and I've seen some Category 4s. You don't even see them that much," Trump said. "But a Category 5, I don't even know if I've heard the term other than I know it's there. That's the ultimate, and that's what we have, unfortunately."