The Hurricane Center forecasts that Florence will approach the coasts of North and SC later on Thursday, then move near or over the coast of southern North Carolina and eastern SC on Thursday night and Friday.
The White House said on Friday that President Donald Trump had spoken with state and local officials, assuring them the federal government was prepared to help.
More than 700,000 people were left without power and millions more were warned by the governor of North Carolina that they were facing "an extremely unsafe situation".
Rain, wind and rising floodwaters from Hurricane Florence swamped the Carolinas early on Friday as the massive storm crawled toward the coast, threatening millions of people with record rainfall and punishing surf.
Downed trees, branches on the hurricane-lashed streets of Wilmington, North Carolina. Gradual weakening is expected throughout the day Friday, with significant weakening predicted over the weekend.
Shaken after seeing waves crashing in the Neuse River just outside his house in the town of New Bern, hurricane veteran Tom Ballance wished he had evacuated.
Once a Category-4 hurricane with winds of 225kph, the hurricane was downgraded to Category 1 on Thursday night.
"This storm is going to continue its violent grind across our state for days", North Carolina Governor Roy Cooper said.
The storm was about 35 miles east of Wilmington, N.C., and about 50 miles southwest of Morehead City, N.C., the National Hurricane Center's 2 a.m. EDT Friday advisory said. As of Friday morning, there were upwards of 20,000 people in 157 shelters across the state of North Carolina, and that number will only continue to climb as rescue efforts are now underway. A 78-year-old man was electrocuted attempting to connect extension cords while another man perished when he was blown down by high winds while checking on his hunting dogs, a county spokesman said.
And cameras aboard the International Space Station managed to catch incredible footage just a few minutes after the storm's landfall.
Richmond, Va. -based Dominion Energy, which provides power in the northeastern corner of North Carolina, was reporting over 1,900 scattered outages.
Florence, which is now a slow-moving Category 2 storm, is expected to linger over the Carolinas before turning north and sliding into western Virginia.
About 70 people were pulled from a motel near Camp LeJeune at the height of the storm as the roof started to collapse.
In New Bern, population 29,000, flooding on the Neuse River left 500 people in peril. Utility companies said millions were expected to lose power and restoration could take weeks.
The total bill for damage from Florence could eventually reach $US10 billion ($13.8b) to $US20 billion ($27.7b), said Chuck Watson, a disaster researcher at Enki Research in Savannah, Georgia. Through noon Friday, 96 stores in the Carolinas and one in Virginia were closed because of the storm.