At 11:00 pm (0300 GMT Thursday), the NHC said Dorian was located 105 miles south of Charleston, South Carolina and moving north at around seven miles per hour approaching the US coast.
Hurricane Dorian, which has left at least 20 people dead in the Bahamas, was upgraded to a Category 3 storm late on Wednesday as it bore down on the southeast US coast, meteorologists said.
The Miami-based National Hurricane Center (NHC) said Dorian, which has already wrought major damage on Grand Bahama and Abaco islands, was packing maximum sustained winds of 115 miles per hour (185 kilometres per hour), making it a Category 3 storm on the five-level scale.
At 11:00 pm (0300 GMT Thursday), the NHC said Dorian was located 105 miles south of Charleston, South Carolina and moving north at around seven miles per hour.
Dorian creeps up US coast; near-record storm surge feared
Some 70,000 people are in need of immediate aid in the Bahamas, which were devastated by Hurricane Dorian, a top UN official said Wednesday, citing food, water, shelter and medicine.
The UN has released $1 million from its emergency fund to provide assistance to victims, Under-Secretary-General for Humanitarian Affairs Mark Lowcock told journalists during a phone call from Nassau.
Officials in the island nation say the death toll has risen to at least 20 and is expected to rise.
Earlier weakened but still deadly, Hurricane Dorian crept up the Southeastern US coast on Wednesday and millions were ordered to evacuate as forecasters said near-record levels of seawater and rain could inundate Georgia and the Carolinas.
The storm, which ravaged the Bahamas with more than a full day of devastating wind and rain, had weakened substantially, from a Category 5 storm to a Category 2, but still had dangerously high winds and threatened to swamp low-lying regions from Georgia to southeastern Virginia as it moved northward.
"We will experience hurricane-force winds, in at least gusts," South Carolina Gov. Henry McMaster said at a news conference Wednesday. Even if the hurricane doesn't end up hitting the state directly, he said, "there's still going to be wind and water and if you're in the coastal area, that water can be treacherous."
Dorian appeared likely to get dangerously near Charleston, which is particularly vulnerable since it is located on a peninsula. A flood chart posted by the National Weather Service projected a combined high tide and storm surge around Charleston Harbor of 3.1 metres; the record, 4 metres, was set by Hugo in 1989.
830,000 people were under mandatory evacuation
Stores and restaurants were boarded up with wood and corrugated metal in the city's historic downtown, and about 830,000 people were under mandatory evacuation orders on the South Carolina coast.
More than 400 people were in state-operated shelters statewide, and more were expected.
Mark Russell, a homeless US Army veteran, said he had been in a shelter since Monday awaiting slow-moving Dorian.
"Once the rain comes and the wind hits, it's going to blow left, right, in and out, and there's not really a place that you can find" to avoid it, said Russell, 63.
In North Carolina, where authorities said an 85-year-old man died after falling from a ladder while getting ready for the storm, Gov. Roy Cooper warned about the threat of storm surge and flash flooding from heavy rains. The Outer Banks were particularly vulnerable.
Georgia's coastal islands were also at risk, Gov. Brian Kemp said Wednesday.
"We are very worried, especially about the barrier islands getting cut off if we have these storm surges at the same time as ... the high tides," Kemp said.
Duke Energy said Dorian could cause more than 700,000 power outages in eastern regions of North Carolina and South Carolina, and Georgia Power said about 2,800 homes and businesses were already without electricity.
The Navy ordered ships at its huge base in Norfolk, Virginia, to head out to sea for safety, and warplanes at Langley Air Force Base in Hampton, Virginia, were being moved inland to Ohio.
Weaker but bigger since it slammed the Bahamas with 295 km/h winds earlier this week, Dorian was moving along Florida's northeastern coast at 13 km/h late Wednesday afternoon. Forecasters said it had maximum sustained winds of 177 km/h and was centered about 241 kilometres south of Charleston.
A hurricane warning covered about 805 kilometres of coastline, and authorities warned about 3 million residents to get away before the water and wind rose with Dorian's approach.
The acting administrator of the Federal Emergency Management Agency, Peter Gaynor, said 4,000 federal responders; 6,000 National Guard members; and 40,000 utility workers were on standby for the hurricane.
"We are ready to go," Gaynor said. "We'll follow Dorian up the coast until it is not a threat to the US"
In Florida, initially projected to take a direct hit from Dorian, there was widespread relief and gratitude on Wednesday after the storm passed the state from a relatively safe distance offshore.
"We're lucky today," said Ryan Haggett, kitchen manager at the Oceanside Beach Bar and Grill, at Flagler Beach on the state's central coast. Haggett and others were removing storm shutters they had placed over the restaurant's windows and planned to serve dinner Wednesday night.
"This storm was much less than what happened two years ago, three years ago with Irma and Matthew," Haggett said, referring to the deadly storms that hit in 2017 and 2016. "They were the worst."
With the threat to Florida easing and the danger shifting northward, Orlando, Florida's international airport reopened, as did Walt Disney World and Universal. Dorian forced Disney Cruise Line to cancel one trip and delay the return of another ship to Port Canaveral, Florida.
One resident in the state died while preparing for the storm Monday evening, when Dorian's path was still projected to include central Florida. Joseph Walden, 56, was sitting on a tree limb and using a chainsaw to trim other limbs in the Orlando suburb of Ocoee when one of the cut limbs broke free and struck him, pushing him to the ground, Ocoee police said in a news release. He was pronounced dead at a hospital.