US forecasters late Thursday downgraded Hurricane Florence to a Category 1 storm, as its outer edge lashed the Carolinas with strong winds and heavy rain.
The big slosh has begun, and the consequences could be disastrous.
Hurricane Florence's leading edge battered the Carolina coast Thursday, bending trees and shooting frothy sea water over streets on the Outer Banks, as the hulking storm closed in with 150 kph winds for a drenching siege that could last all weekend.
US forecasters late Thursday downgraded Hurricane Florence to a Category 1 storm.
In its 0300 GMT advisory, the National Hurricane Center said the maximum sustained winds of Florence were 150 kph, dropping it to the weakest of five categories on the Saffir-Simpson scale.
But the storm still carried "very dangerous winds," the Center added.
On Wednesday, Florence was downgraded twice from its peak as a Category 4 storm which causes "catastrophic damage."
But Brock Long, the administrator of the Federal Emergency Management Agency, has warned residents to take the storm seriously no matter what the category.
Forecasters continue to warn of storm surges, excessive rainfall and catastrophic flash flooding.
Winds and rain were arriving later in South Carolina, and a few people were still walking on the sand at Myrtle Beach while North Carolina was getting pounded.
Nicole Johnston has more on the story from Wilmington, North Carolina.
North Carolina Governor Roy Cooper warned: "Don't relax, don't get complacent. Stay on guard. This is a powerful storm that can kill. Today the threat becomes a reality."
More than 80,000 people were already without power as the storm approached, and more than 12,000 were in shelters. Another 400 people were in shelters in Virginia, where forecasts were less dire.
Forecasters said that given the storm's size and sluggish track, it could cause epic damage akin to what the Houston area saw during Hurricane Harvey just over a year ago, with floodwaters swamping homes and businesses and washing over industrial waste sites and hog-manure ponds.
"It truly is really about the whole size of this storm," National Hurricane Center Director Ken Graham said. "The larger and the slower the storm is, the greater the threat and the impact — and we have that."
Giles Gibson joins TRT World from North Carolina's Wilmington, a place very much on the storm's path.
The hurricane was seen as a major test for the Federal Emergency Management Agency, which was heavily criticised as sluggish and unprepared for Hurricane Maria in Puerto Rico last year.
As Florence drew near, President Donald Trump tweeted that FEMA and first responders are "supplied and ready," and he disputed the official conclusion that nearly 3,000 people died in Puerto Rico, claiming the figure was a Democratic plot to make him look bad.
Schools and businesses closed as far south as Georgia, airlines canceled more than 1,500 flights, and coastal towns in the Carolinas were largely emptied out.
Around midday, Spanish moss blew sideways in the trees as the winds increased in Wilmington, and floating docks bounced atop swells at Morehead City. Some of the few people still left in Nags Head on the Outer Banks took photos of angry waves topped with white froth.
Wilmington resident Julie Terrell was plenty concerned after walking to breakfast past a row of shops fortified with boards, sandbags and hurricane shutters.
"On a scale of 1 to 10, I'm probably a 7" in terms of worry, she said. "Because it's Mother Nature. You can't predict."
Forecasters' European climate model is predicting 2 trillion to 11 trillion gallons of rain will fall on North Carolina over the next week, according to meteorologist Ryan Maue of weathermodels.com. That's enough water to fill the Empire State Building nearly 40,000 times.
More than 1.7 million people in the Carolinas and Virginia were warned to evacuate over the past few days, and the homes of about 10 million were under watches or warnings for the hurricane or tropical storm conditions.
Homeless after losing her job at Walmart three months ago, 25-year-old Brittany Jones went to a storm shelter at a high school near Raleigh. She said a hurricane has a way of bringing everyone to the same level.
"It doesn't matter how much money you have or how many generators you have if you can't get gas," she said. "Whether you have a house or not, when the storm comes it will bring everyone together. A storm can come and wipe your house out overnight."
Duke Energy Co. said Florence could knock out electricity to three-quarters of its 4 million customers in the Carolinas, and outages could last for weeks. Workers are being brought in from the Midwest and Florida to help in the storm's aftermath, it said.
A buoy off the North Carolina coast recorded waves nearly 9 metres high as Florence churned toward shore.
Scientists said it is too soon to say what role, if any, global warming played in the storm. But previous research has shown that the strongest hurricanes are getting wetter, more intense and intensifying faster because of human-caused climate change.
Florence's weakening as it neared the coast created tension between some who left home and authorities who worried that the storm could still be deadly.
Frustrated after evacuating his beach home for a storm that was later downgraded, retired nurse Frederick Fisher grumbled in the lobby of a Wilmington hotel several miles inland.
"Against my better judgment, due to emotionalism, I evacuated," said Fisher, 74. "I've got four cats inside the house. If I can't get back in a week, after a while they might turn on each other or trash the place."
Authorities pushed back against any suggestion the storm's threat was exaggerated.
The police chief of a barrier island in Florence's bulls'-eye said he was asking for next-of-kin contact information from the few residents who refused to leave.
"I'm not going to put our personnel in harm's way, especially for people that we've already told to evacuate," Wrightsville Beach Police Chief Dan House said.