It fell from the strength of the hurricanes when it landed on land, but forecasters said the 350-mile storm's slow progress through North Carolina and South Carolina could leave most of the region underwater in the next days.
"This storm is relentless and unbearable," North Carolina Gov. Roy Cooper told CNN on Friday. "There probably is not a county or a person that is not affected in some way by this massive and violent storm."
A mother and her baby were killed when a tree fell at their home in Wilmington, North Carolina. The injured father of the child was taken to the hospital. In Pender County, a woman died of a heart attack; the paramedics who were trying to reach it were blocked by debris.
Two people died in Lenoir County. A 78-year-old man was electrocuted while trying to connect extension cords while another man died when he was knocked down by strong winds while checking his hunting dogs, a county spokesman said.
In New Bern, North Carolina, the storm surge surpassed the city of 30,000 that lies at the confluence of the Neuse and Trent rivers.
Officials in New Bern, dating from the early 18th century, said more than 100 people were rescued from the floods and that the city center was under water on Friday afternoon.
Resident Jay Manning said he and his wife watched in alarm as water filled the street.
"We moved all the furniture in case the water came in, but the water seems to be at the edge of the driveway," he said, adding that if the wind blows and the rain keeps coming, that could change. "My wife is in a panic at this time."
Dan Eudy said he and his brother were woken up Thursday night by the sound of a boat crashing into his front porch.
Eudy said her family stayed at home partly to protect her home. "And we did not think it would be as significant an event as it was," he said. "This is an event of 500 or 1,000 years."
Florence was a category 3 hurricane on the five-step Saffir-Simpson scale with winds of 120 mph on Thursday. It was demoted to a Category 1 hurricane before reaching the coast near Wrightsville Beach, near Wilmington, North Carolina.
The National Hurricane Center (NHC) lowered it to a tropical storm on Friday, but warned that it would drop between 30 and 40 inches (76-102 cm) of rain on the southeastern coast of North Carolina and part of northeast Carolina. South.
Around 10 million people could be affected by the storm.
More than 22,600 people were housed in 150 shelters throughout the state, including schools, churches and the Wake Forest University basketball stadium.
"This rain will produce catastrophic flash floods and prolonged and significant flooding in rivers," the hurricane center said.
Atlantic Beach on the Outer Banks of North Carolina had already received 30 inches of rain, the US Geological Survey said, while more than 25 inches have fallen in the Newport, Morehead City area since Thursday.
Public services in North Carolina estimated that up to 2.5 million state residents could be without power, the state Department of Public Safety said.
The White House said Friday that President Donald Trump had spoken with state and local officials, assuring them that the federal government was ready to help. Trump plans a visit to the region next week.
Florence moved west-southwest at approximately 5 mph (7 km / h), with its center located in eastern South Carolina. The storm is expected to turn west and then north moving through the Carolinas and the Ohio Valley by Monday, the NHC said early on Saturday.
The storm was expected to turn into a tropical depression on Saturday and a significant weakening was expected over the weekend, the NHC said in a bulletin.
Florence was one of the two great storms that threatened millions of people on opposite sides of the world.
Super typhoon Mangkhut crossed the northern tip of the Philippines on Saturday packing winds of more than 200 km per hour (124 mph) along with torrential rains, killing three people and causing floods, landslides and power outages.