Forecasters said the Category 1 storm's extreme size meant it could batter the U.S. East Coast with hurricane-force winds for almost a full day.
"I feel like the dumbest human being who ever walked the face of the earth", said Ballance, owner of a seafood restaurant that was flooded. The storm was moving west-northwest at 10 miles per hour with winds that have decreased significantly to 100 miles per hour.
"It truly is really about the whole size of this storm", National Hurricane Center Director Ken Graham told The Associated Press.
The NHC said the threat of tornadoes was increasing as Florence neared shore and South Carolina Governor Henry McMaster said the heavy rain could trigger landslides in the west of his state.
The rising sea crept towards the two-storey home of Tom Copeland, who lives on a spit of land surrounded by water in Swansboro.
The result: prolonged storm surge, wind and rain. As Cooper said, "There's nowhere for the water to go".
He said only about 300,000 of the 700,000 people who live in the mandatory evacuation zone have left. The storm was a unsafe Category 4 hurricane Wednesday but was downgraded Thursday night to a Category 1 storm.
In Craven County, authorities say they have received more than 150 telephone calls from people in the historic town of New Bern asking to be rescued because water has entered their homes.
Nearly 20,000 people had taken refuge in 157 emergency shelters, Cooper said.
Florence made landfall as a Category 1 hurricane at 7:15 a.m.at Wrightsville Beach, a few miles east of Wilmington and not far from the SC line, coming ashore along a mostly boarded-up, emptied-out stretch of coastline.
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Millions of people have evacuated to inland communities as the storm churns westward.
In New Bern, where rescuers removed more than 100 people from rising waters, Sarah Risty-Davis is one of the residents who chose to ignore a mandatory evacuation order issued three days ago.
Employees at New Bern's WCTI-TV NewsChannel 12 had to abandon their studio for the "first time in history", the station posted on Facebook Thursday night.
The Wilmington airport had a wind gust clocked at 105 miles per hour (169 kph), the highest since Hurricane Helene in 1958, the weather service said. At the city's airport, the wind was gusting at 91 miles per hour.
As of 8am ET on Thursday, Florence was driving maximum sustained winds of 110mph (177km/h), according to an updated forecast from the National Hurricane Center. More than 3,000 inmates at North Carolina prisons and juvenile detention centres were moved out of the storm's path.
It was expected to begin pushing its way westward across SC later in the day, in a watery siege that could go on all weekend. That's down from a high of 140mph, but still expected to cause "life-threatening storm surge and rainfall".
He added that Hurricane Florence poses a challenge because it is expected to drift over hard-hit areas. "The building has been evacuated, just so that you know", he said.
This will take place heading into early next week.
To prepare for this storm, businesses have been boarding up, and supplies have been readied for what is expected to be a large-scale relief operation.
A state of emergency has been declared in five coastal states - North Carolina, South Carolina, Georgia, Maryland and Virginia. Thousands of soldiers from their National Guard forces have been mobilized. Cooper said he hopes more shelters will also open today. The storm may gradually drift into northeast SC.
While forecasters have been keeping a close eye on the storm from the ground, the International Space Station watched the slow-moving hurricane make landfall from above. Its designation then was "potential tropical cyclone six".