Hurricane Florence is the strongest storm to target the Carolinas and Virginia region "in decades," federal emergency officials said Tuesday in issuing dire warnings for the hundreds of thousands of people ordered to evacuate before the Category 4 storm makes landfall.

Hurricane warnings or watches are affecting areas along the coast with an estimated population of more than 5.4 million, according to data from the National Weather Service. A storm surge warning was in place from an area north of Charleston to part of North Carolina's Outer Banks.

North Carolina Gov. Roy Cooper was adamant Wednesday that residents in evacuation areas flee before tropical storm force winds begin whipping ashore Thursday. The state has begun mobilizing emergency supplies and equipment, including bulldozers and chainsaws, in place for the storm's aftermath.

Cooper said on "Today" that he's most worried about the size of Florence — a "vicious" storm bigger than the state of Michigan — and how much uncertainty there remains with rainfall and flooding.

"We know that this storm as soon as it hits the North or South Carolina coast, it's going to hang around," Cooper said. "That's when you start measuring rain in feet and not in inches."

Jeffrey Byard, the Federal Emergency Management Agency's associate administrator for response and recovery, warned Tuesday that Florence is "the strongest storm to target the Carolinas and this part of our country in decades."

There was nothing currently projected to slow down or weaken the storm, he added, and FEMA was expecting "massive damage," including power outages and infrastructure damage.

As of Wednesday morning, the storm was about 530 miles southeast of Cape Fear, North Carolina, and moving west-northwest at 17 mph with 130-mph maximum sustained winds, according to the National Hurricane Center. The storm was expected to bring life-threatening storm surge and rainfall to portions of the Carolinas and the Mid-Atlantic.

Hurricane and storm surge warnings were issued from South Santee River, South Carolina, to Duck, North Carolina, and the Albermarle and Pamlico Sounds. A tropical storm watch was also issued from north of the North Carolina-Virginia border to Cape Charles Light, Virginia, and for the Chesapeake Bay south of New Point Comfort.

The warnings mean there is a possibility of life-threatening inundation from rising water moving inland from the coastline and hurricane conditions.

Allison Violette, a resident of Fayetteville, North Carolina, said she and her husband were moving their belongings to the second floor of their home after Hurricane Matthew flooded the house in 2016.

"It's devastating to walk into your house and have seen it flooded, and to lose everything. And to think that can happen again, I just don't, I just don't want to have that. And so anything I can save that's meaningful for us, I want to save it," she said.

"I don't know if we would want to do that again, and experience it. It's just life-changing," said her husband Cal Violette.

The first outer rain bands from Florence could move into the Outer Banks of North Carolina, South Carolina and southeast Virginia on Wednesday night, said FEMA's National Oceanic and Atmospheric Administration liaison Steve Goldstein.

Hurricane-force winds could extend inland into central North Carolina and central Virginia later in the day on Thursday and a large area of tropical storm-force winds were expected to last until Friday, he added.

Florence is expected to approach the coast of the Carolinas around Friday morning, according to NBC News meteorologist Bill Karins. The storm is expected to stall around Friday into Sunday, but still could potentially lead to both historic rainfall and severe inland flooding, Karins said.

Goldstein predicted potential rainfall totals of 15 to 20 inches.

Cooper extended a mandatory evacuation in the state to the Outer Banks barrier islands during a Tuesday afternoon news conference warning civilians to prepare for the major storm and heed evacuation orders.

Earlier Tuesday, South Carolina Gov. Henry McMaster lifted a mandatory noon evacuation deadline for the southern counties of Beaufort, Colleton and Jasper, with the exception of Edisto Beach, based on updated forecast predictions. Evacuations remained mandatory for the rest of the coast.

The mayor of Washington, D.C., declared a state of emergency on Tuesday, joining governors of South Carolina, North Carolina, Virginia and Maryland. West Virginia has declared a state of preparedness.

President Donald Trump said Tuesday that the government and FEMA were prepared to respond to the storm, but acknowledged there was a chance the storm could strongly hit the East Coast.

"We are absolutely and totally prepared," he said.

Myrtle Beach, South Carolina, resident Maria Nichols said she was preparing to board up her home and evacuate after having gone through several storms in the past.

"I'm about 150 yards from the ocean. They are boarding us up right now and I'm leaving," she said.

She added that she was "absolutely not" taking any chances.

"It doesn't matter if it doesn't hit us, they said we need to leave it's important for us to evacuate, we don't need to take chances, we don't need to put personnel on the line and to come and try and save us," Nichols said.

But Loraine and Mark Taylor, who also live in an evacuation zone in Myrtle Beach, said they would be riding out the storm.

"I've been through a lot of storms and we feel like that this is our home," Loraine Taylor said. "We're just going to stay here and protect our own stuff."

She added that the community they live in has a lot of retired residents and she and her husband wanted to stay behind in case they needed help.

In Fayetteville, Al Miller said he was worried that Blounts Creek would overflow and flood his home. The last time, eight feet of water rose in about half an hour, he said, and fears that development has put an even greater strain on the waterway. "Nine of us, flooded out. Twenty-six houses were flooded in this area," Miller said. "And nothing’s been done to fix it."

But Miller's wife works for the utility company and will be working during the storm, and he will stay to try and protect their house and check on neighbors. They moved their two dogs to a friend's house where they will be safe."

"If it floods, I'll do the best I can do to save what I can save," Miller said. "And then I’ll get out and I’ll check on everybody else."