More than 80,000 people were already without power as the storm approached, and more than 12,000 were in shelters.
Sarah Risty-Davis, a resident of New Bern, tells NPR she had water up to the second floor in her 1920s-era home near Neuse River.
"WE ARE COMING TO GET YOU", New Bern city officials said on Twitter.
As the giant, 644km/hr hurricane pounded away, it unloaded heavy rain, flattened trees, chewed up roads and knocked out power to more than 600,000 homes and businesses.
The National Hurricane Centre said a gauge in Emerald Isle, North Carolina, reported 6.3 feet (1.92 metres) of inundation. But the danger comes not so much from the wind as from the storm surges, which could raise the sea level to 4 meters in some points and flood the coast.
"To those in the storm's path, if you can hear me, please stay sheltered in place", he said at a news conference in Raleigh, adding that Florence would "continue its violent grind across the state for days".
The station reported the fourth death involved a 77-year-old Kinston man who family members said died at 8 a.m. Friday when he was "blown down by the wind" while tending dogs.
"It truly is really about the whole size of this storm", National Hurricane Center Director Ken Graham said.
As Hurricane Florence unleashes a deluge upon North Carolina, the city of New Bern has found itself inundated with floodwater, forcing hundreds of residents to call for help.
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.
Authorities said more than 60 people, including many children and pets, had to be evacuated from a hotel in Jacksonville, North Carolina, after strong winds caused parts of the roof to collapse.
Still, he said: "I feel like the dumbest human being who ever walked the face of the earth".
Atlantic Beach was receiving winds of roughly 65-75 miles per hour as of 3:30 p.m. Thursday, according to a Fox News report. The company, which recently hit a $1 trillion valuation, also donated 100,000 food items and more than 30,000 bottles of water to Feeding America, Amazon announced in a blog post.
"This is an absolute life-threatening scenario".
With many employees at risk, Novartis said it has temporarily stopped pharmaceutical production at their Wilson, North Carolina site.
Prior to Hurricane Florence's landfall, more than 1.7 million were ordered to evacuate the coast.