In mountainous, hard-hit Buncombe County, which includes the city of Asheville, 35 people have died, the county sheriff said at a news briefing on Monday.
The county was set to begin distributing food and water later in the day to residents, after some supplies were airlifted to the region that has been largely isolated by flooded roads and power outages.
Storm surges, heavy rainfall and devastating winds have wreaked havoc on southeastern states. (AP PHOTO)
"We don't have water, and we do not have power across most of the county... the roads are still incredibly dangerous," County Manager Avril Pinder said.
In neighbouring Yancey County, the storm snapped century-old trees around the home of Taylor Shelton, 44. It took her husband two days with a chainsaw to cut a passage through the felled trees in their driveway and the nearby road so they could drive themselves and their three children out of the darkened house.
"The devastation is unbelievable," she said in a phone interview.
She has still not been able to reach her husband's parents, who live in the nearby town of Burnsville, which was also badly hit.
"It looks like War of the Worlds, very, very big trees are down everywhere," she said.
"We saw houses that are just washed away."
Some 2.1 million homes and businesses have been left without power. (AP PHOTO)
Mobile service remained out in large swaths from Ohio through the Carolinas and into Florida. Some 2.1 million homes and businesses were without power early on Monday, according to the website Poweroutage.us.
"The lack of communication is concerning," North Carolina Governor Roy Cooper said on Monday in an interview with CNN.
"We know that there are people missing, and we know that there's going to be significant fatalities at the end of this and our prayers and our hearts go out to these families."
Cooper, who said he had not heard from his son and daughter in 72 hours, added that local officials and rescue workers were performing door-to-door welfare checks in many communities.
In Buncombe, officials said they are conducting checks of 150 "priority" households that include elderly residents or residents with medical problems.
The National Guard and emergency workers from 19 states have been deployed to help, along with Federal Emergency Management Agency personnel. Cooper said the rugged terrain in the mountains of western North Carolina makes it almost impossible to traverse with landslides and flooding.
"So we're depending a lot on air power, helicopters with hoist capacity to get supplies in," he said.
President Joe Biden said he would visit North Carolina later this week and may ask Congress to return to Washington for a special session to pass supplemental aid funding.
"There's nothing like wondering, 'is my husband, wife, son, daughter, mother, father, alive?'" Biden said at the White House.
"Many more will remain without electricity, water, food and communications, and whose homes and businesses are washed away in an instant. I want them to know we're not leaving until the job is done."
President Joe Biden will visit North Carolina and may ask Congress for supplementary aid funding. (AP PHOTO)
Vice President and Democratic presidential candidate Kamala Harris cut short a campaign trip in Nevada on Monday to take part in briefings in Washington on the hurricane response and will visit the region when doing so won't impede response efforts, a White House official said.
Republican presidential candidate Donald Trump will visit Valdosta, Georgia, on Monday to receive a briefing on storm damage.
Helene slammed into Florida's Gulf Coast on Thursday night, triggering days of driving rain and destroying homes that had stood for decades. As it moved north it washed out roads, decimated neighbourhoods and left many communities without water and basic necessities.
The death toll was over 100 in the Carolinas, Georgia, Florida, Tennessee and Virginia, and likely to rise.
Damage estimates ranged from $US15 billion to more than $US100 billion ($A22b to $A144b), insurers and forecasters said over the weekend, as water systems, communications and critical transportation routes were damaged or destroyed.
