Hurricane Joaquin has barrelled through the Bahamas as an extremely dangerous Category Four storm, while jittery residents in the eastern United States battened down.
Joaquin was packing maximum sustained winds of 215km/h and could grow even stronger over the next 24 hours, the National Hurricane Centre said.
"On the forecast track, the core of strongest winds of Joaquin will move near or over portions of the central Bahamas [late Thursday (local time)] and pass near or over portions of the northwestern Bahamas on Friday," the NHC said.
It described Joaquin as a large storm moving at only 7km/h.
"Hurricane-force winds extend outward up to 50 miles (80km) from the centre and tropical-storm-force winds extend outward up to 185 miles (295km)," the bulletin said.
The storm has potential for life-threatening damage, and on its current path was likely to cause coastal flooding in the mid-Atlantic US region, forecasters said.
Emergency preparations began as far north as New York, and officials in the Bahamas urged people to brace for up to 37cm of rain.
In Virginia, which was already hit by flash flooding on Tuesday, the governor declared a state of emergency to prepare for more rain even before Joaquin arrives. Authorities in New Jersey did the same.
Joaquin is the third hurricane of the 2015 Atlantic season, which began in June and ends in November. Peak activity usually occurs in September.