The storm has sustained wind speeds of 90 miles per hour, and 40 inches of rain could fall over the next few days, according to the National Hurricane Center. Tens of thousands were without power.
Its surge could cover all but a sliver of the Carolina coast under as much as 3.4 metres of ocean water, and days of downpours could unload more than 900mm of rain, triggering severe flooding. The storm has weakened to a Category 1, with wind speeds of 90 miles per hour.
"Florence is an uninvited brute who doesn't want to leave", North Carolina Gov. Roy Cooper told NPR's Morning Edition.
More than 80,000 people were already without power as the storm began buffeting the coast, and more than 12,000 were in shelters. Another 400 people were in shelters in Virginia, where forecasts were less dire.
There are fears that this storm could cause damage similar to what Houston suffered during Hurricane Harvey a year ago, when homes and businesses were inundated with floodwater.
Because a large section of the storm will remain over the water, and it's even possible the center drifts back over the ocean, its weakening will be very slow on Friday.
THE life-threatening hurricane, Florence, is expected to hover the Carolinas in the USA with torrential rains, high winds and massive coastal erosion.
It's unclear exactly how many people fled, but more than 1.7 million people in the Carolinas and Virginia were warned to clear out.
Around midday, Spanish moss blew sideways in the trees as the winds increased in Wilmington, and floating docks bounced atop swells at Morehead City.
Wilmington resident Julie Terrell was plenty concerned after walking to breakfast past a row of shops fortified with boards, sandbags and hurricane shutters.
"This is my third hurricane that I have worked, my second one with Craven County", she says. "Because it's Mother Nature".
National Weather Service forecaster Brandon Locklear predicted Florence would drop up to eight months' worth of rain in two or three days.
Time is running short to get out of the way of Hurricane Florence, a monster of a storm that has a region of more than 10 million people in its potentially devastating sights.
She said a hurricane has a way of bringing everyone to the same level. "I have never seen a hurricane that is literally going to be with us for two days", he said. Workers are being brought in from the Midwest and Florida to help in the storm's aftermath, it said. Storm surge search and rescue operations have been underway across the county. Utility companies said millions were expected to lose power and restoration could take weeks.
Being such a small number, first responders have made clear to them the situation when the storm makes its expected complete landfall by 8 a.m. Friday morning.
The NHC said hurricane-force winds extended outward 80 miles from the center of the storm and tropical storm-force winds extended almost 195 miles out.
Power suppliers report more than 350,000 outages in North Carolina, the bulk along the coast. But previous research has shown that the strongest hurricanes are getting wetter, more intense and intensifying faster because of human-caused climate change.