North Carolina, South Carolina, Virginia, and Maryland and Columbia (Washington DC) have all declared states of emergency. Heavy rain, storm surge, damaging winds, rough surf and isolated tornadoes will be possible, especially in eastern North Carolina.
The storm's winds may have weakened in recent days - they are now at 110mph (175km/h) - but there are fears Florence's slow-moving nature could bring different problems.
Model data shows Florence being a very patient storm. "Hurricane-force winds extend outward up to 80 miles (130 km) from the centre and tropical-storm-force winds extend outward up to 195 miles (315 km)".
With South Carolina's beach towns now more in the bull's-eye because of the shifting forecast, OH vacationers Chris and Nicole Roland put off their departure from North Myrtle Beach to get the maximum amount of time on the sand.
Accuweather reported that its meteorologists "believe that the hurricane will stall and meander near the Carolina coast from Thursday night to Saturday".More news: "No-deal" Brexit would complicate driving, data and roaming, United Kingdom says
But it will be the rain and flash flooding that likely will have the most devastating impact, officials said.
Little change in strength is expected before the center reaches the coast, with weakening expected after the center moves inland.
"It doesn't matter where you are", he said.
Hurricane Florence is expected to make landfall in North Carolina late Thursday night or Friday morning. Currently, the hurricane-force winds extend outward 80 miles from the center and tropical storm-force winds extend almost 200 miles from the eye.
Some forecasters have predicted it could be the most powerful storm ever to hit the region.More news: Ariana Grande Posts Heartbreaking Statement About Mac Miller
We continue to keep an eye on Hurricane Florence as the storm inches closer to the southeast coast. "Significant river flooding is expected as a result of excessive rainfall across area hydrologic basins".
The main threat from this storm will likely be inland flooding. "This is a life-threatening situation", the advisory said. That means locals and their property could be punished with severe hurricane conditions for days, not hours.
SC governor Henry McMaster said earlier this week in a statement: "Now is the time for your family also to prepare and stay tuned for more updates".
Numerous communities throughout the region have issued either mandatory or voluntary evacuation orders.
More than 1 million people have been ordered to evacuate and authorities urged them to get going before the streets become inundated.More news: Met Office: Isaac now a weak tropical storm