Videos and images posted to social media show the extent of hurricane conditions across the Carolinas and Mid Atlantic states.
Rushing water can be seen gushing through streets reaching windows, trees are bending with the force of 90mph winds, and dark clouds are ominously hanging over affected areas.
The path of Florence will make the dangerous weather conditions last for days, as it has slowed down upon reaching land.
At 7.15am local time (12.15pm BST), hurricane Florence made landfall, with the eye of the storm hitting close to Wrightsville Beach in North Carolina.
Latest observations place the hurricane about five miles east of Wilmington, North Carolina – with maximum sustained wind speeds of 90mph.
These wind speeds place Florence at a category one hurricane, but despite the low categorisation, the amount of rain and strong storm surges mean extensive damage will be caused.
“Storm surge inundation near the coast, extreme winds, historic flooding rainfall, and prolonged life-threatening river flooding are expected.”
As the storm progresses the NHC says: “Catastrophic freshwater flooding expected over portions of North and South Carolina.”
Rivers have already burst their banks in some areas with the Neuse River in New Bern, North Carolina yesterday spewing water over its banks and into nearby streets.
There have been no immediate reports of storm-related deaths or serious injuries, but officials said more than 100 people were rescued in New Bern, as the downtown area of the city was under water.
The contents of the Pungo River in Belhaven, North Carolina have also overflowed and swelled dangerously.
Videos on social media show the water reaching the windows of some houses in the Belhaven area.
“You may need to move up to the second story, or to your attic, but WE ARE COMING TO GET YOU.”
Almost 20,000 residents are taking shelter in 157 emergency shelters according to North Carolina governor Roy Cooper.
A further 370,000 people are without power in North Carolina today, state officials said.
Utility companies have predicted that millions are expected to lose power and that restoring it could take weeks.