US East Coast residents are running out of time to flee before Hurricane Florence batters the region, officials have warned.
Up to 1.7 million people have been ordered to evacuate across South Carolina, North Carolina and Virginia.
South Carolina authorities have turned four motorways into one-way routes away from the coast to speed the exodus.
The category four storm with 130mph (215km/h) winds is forecast to make landfall early on Friday.
A National Weather Service forecaster in Wilmington, North Carolina, said: “This will likely be the storm of a lifetime for portions of the Carolina coast.
“And that’s saying a lot given the impacts we’ve seen from Hurricanes Diana, Hugo, Fran, Bonnie, Floyd and Matthew.
“I can’t emphasise enough the potential for unbelievable damage from wind, storm surge and inland flooding with this storm.”
As well as in the Carolinas and Virginia, states of emergency have been declared in Maryland and Washington DC.
Jeff Byard, of the Federal Emergency Management Agency, said: “This is going to be be a Mike Tyson punch to the Carolina coast.”
North Carolina Governor Roy Cooper warned citizens that a “disaster is at the doorstep”, and that “tens of thousands” of buildings are likely to be flooded.
A National Hurricane Center (NHC) plane flying inside the storm found that pressure is continuing to drop, indicating its strength may still be growing.
Waves measuring 83ft (25m) tall were recorded at sea on Wednesday morning.