WILMINGTON, US   -  Georgia declared a state of emergency on Wednesday as forecasters warned of torrential rain in the southern state after Hurricane Florence slams into the Carolinas with what an emergency management official called the force of a “Mike Tyson punch.”

The National Hurricane Center (NHC) said meanwhile that Florence’s maximum sustained winds had eased slightly and it had been downgraded to a Category 3 storm from a Category 4 on the five-level Saffir-Simpson wind scale.

The NHC stressed, however, that while a slow weakening is expected over the next 24 hours “Florence is still forecast to be an extremely dangerous major hurricane when it nears the US coast late Thursday and Friday.” As Florence churned across the Atlantic packing winds of 125 miles per hour (205 kph), President Donald Trump and state officials stepped up appeals to residents in the path of the monster storm to evacuate before it is too late.

“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.

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 after it makes landfall in North and South Carolina.

“This rainfall would produce catastrophic flash flooding and significant river flooding,” the 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, warning of power outages, road closures, infrastructure damage and potential loss of life.

At 2:00 pm (1800 GMT), the eye of the storm was 435 miles (700 kms) southeast of Wilmington, North Carolina, moving northwest at 16 mph (26 kph).

The storm was heading for the coast of North and South Carolina but heavy rain was also expected in Virginia to the north and Georgia to the south.

Georgia Governor Nathan Deal declared a state of emergency “in light of the storm’s forecasted southward track after making landfall.”

“The state is mobilizing all available resources to ensure public safety,” Deal said. “I encourage Georgians to be prepared for the inland effects of the storm as well as the ensuing storm surge in coastal areas.”

A state of emergency has also been declared in Maryland, North Carolina, South Carolina, Virginia and Washington.

People fleeing coastal North and South Carolina clogged highways 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 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 to the south.

“If I need to evacuate I can go to my son’s house” in North Carolina, Sparks said as he carted a load of water bottles to his car.

“He was thinking of coming here until this morning, and now he asked me if I wanted to come up there,” he 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.”

In a trailer park outside Wilmington, Alondra Espinoza was preparing to leave with her two young children.

“Everything is packed,” Espinoza said. “I want to get them as far away as possible.

“I’ve been through hurricanes before but never with kids,” she said. “If it wasn’t for them, I wouldn’t have minded staying here.”

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 ordered the mandatory evacuation of one million coastal residents while North Carolina ordered an evacuation of the Outer Banks, barrier islands that are a popular tourist destination.

In Virginia, 245,000 coastal residents were ordered to evacuate.

Florence is being trailed in the Atlantic by two other storms - Hurricane Helene and Tropical Storm Isaac.

Helene was weakening, however, and posed no danger to land, the NHC said, while Isaac could bring heavy rain to Martinique, Dominica and Guadeloupe.