Hurricane Florence churned across the Atlantic Ocean on Wednesday packing winds of 130 miles per hour (215 kph) as an emergency management official warned the monster storm would deliver a "Mike Tyson punch" to the Carolina coast.
President Donald Trump urged residents to heed orders to evacuate and said the federal government was "ready for the big one that is coming."
"Get out of its way, don't play games with it, it's a big one, maybe as big as they've seen," Trump said. "We'll handle it. We're ready, we're able.
"But despite that, bad things can happen when you are talking about a storm this size," he added.
Florence is currently a Category 4 storm on the five-point Saffir-Simpson hurricane wind scale and is forecast to slam into the Carolinas late Thursday or early Friday.
Up to 1.7 million people are under voluntary or mandatory evacuation orders, and coastal residents were frantically boarding up homes and businesses and hitting the road on Wednesday as the storm approached.
Florence is forecast to dump up to three feet (almost a meter) of rain in some areas.
"This rainfall would produce catastrophic flash flooding and significant river flooding," the Miami-based National Hurricane Center (NHC) said.
Life-threatening storm surges of up to 13 feet (3.9 meters) were also forecast in some areas of North Carolina along with the possibility of tornadoes.
"This is going to be a Mike Tyson punch to the Carolina coast," said Jeff Byard, the associate administrator for response and recovery at the Federal Emergency Management Agency (FEMA).
"This is not going to be a glancing blow," Byard said at a press conference in Washington, warning of power outages, road closures, damage to infrastructure and potential loss of life.
At 11am (1600 GMT), the eye of the storm was about 485 miles (785 kms) southeast of Wilmington, North Carolina, moving in a northwest direction at 15 mph (24 kph).
The storm looked likely to make landfall on the coast of North and South Carolina but heavy rain was also expected in Virginia to the north and Georgia to the south.
STATE OF EMERGENCY
A state of emergency has been declared in Maryland, North Carolina, South Carolina, Virginia and Washington amid concern over potential torrential rain and flooding.
People fleeing coastal North and South Carolina clogged highways early Wednesday as Florence bore down on the coast for a direct hit in a low-lying region dense with beachfront vacation homes.
The eastbound lanes of several major highways have been shut down to allow traffic to flow inland, but the exodus was slow along roads jammed with outward-bound vehicles.
In Columbia, South Carolina, Barry Sparks, a 66-year-old retiree, was thinking of getting out after the path of the storm shifted somewhat to the south.
"If I need to evacuate I can go to my son's house," Sparks said as he carted a load of water bottles to his car. "He lives in North Carolina.
"He was thinking of coming here until this morning, and now he asked me if I wanted to come up there," he said.
"I do worry though about people here because many didn't prepare, you know, because originally they didn't think it was going to be so bad here," Sparks said.
Kevin Miller, a 50-year-old electrician, said he planned to ride out the storm at his home near Charleston.
"I rode out Hugo," Miller said of a 1989 hurricane that caused widespread damage. "The water level will get a little high but we'll be fine.
"Hugo was a direct hit," he said. "I was in the same house and it stood fine. We have everything. We're ready."
North Carolina Governor Roy Cooper warned residents that time was running out to seek safety from what he called a "once in a lifetime" storm.
"Disaster is at the doorstep and is coming in," Cooper said. "If you are on the coast, there is still time to get out safely."
South Carolina Governor Henry McMaster has ordered the mandatory evacuation of one million coastal residents while neighboring North Carolina ordered an evacuation of the Outer Banks, barrier islands that are a popular tourist destination, and parts of coastal Dare County.
In Virginia, 245,000 coastal residents were ordered to evacuate, including from the Eastern Shore.
At this height of the Atlantic hurricane season, Florence was being trailed on east-to-west paths by two other storms, Hurricane Helene and Tropical Storm Isaac.
The NHC said Helene was weakening, however, and posed no danger to land. Isaac could bring heavy rainfall to Martinique, Dominica and Guadeloupe.