Hurricane Florence, on track to become the first Category 4 storm to make a direct hit on North Carolina in six decades, is howling closer to shore, threatening to unleash deadly pounding surf, days of torrential rain and severe flooding.
Fierce winds and massive waves are expected to lash the coasts of North and South Carolina and Virginia even before Florence makes landfall on Friday, and its rains will take a heavy toll for kilometres inland, the National Hurricane Center in Miami warned on Tuesday.
Although Florence is still days from arrival, authorities have taken extraordinary measures to move people out of harm's way. More than one million residents have been ordered to evacuate from coastal areas of the three states, closing university campuses, schools and factories.
Packing maximum sustained winds of 225km/h, the storm ranked as a Category 4 on the five-step Saffir-Simpson hurricane scale and was expected to grow stronger and larger over the next few days, the NHC said.
"This storm is a monster," North Carolina Governor Roy Cooper said. "Even if you've ridden out storms before, this one is different. Don't bet your life on riding out a monster."
He cited forecasts showing Florence was likely to stall over North Carolina, "bringing days and days of rain."
To hasten evacuations from coastal South Carolina, officials reversed the flow of traffic on some highways so all major roads led away from shore. Miles of traffic slowed to a crawl along the main highway along North Carolina's Outer Banks barrier islands.
Maps of Florence's trajectory showed the centre of the storm most likely to strike the southern coast of North Carolina. The last Category 4 hurricane to plow directly into North Carolina was Hazel in 1954, a devastating storm that killed 19 people and destroyed some 15,000 homes.
But NHC spokesman Dennis Feltgen stressed the effects of Florence would be widely felt. Tropical storm-force winds would extend nearly 300 km across three states. A hurricane warning was posted for most of the Carolina coast north to the Virginia border.
In addition to flooding the coast with wind-driven storm surges of seawater as high as four metres, Florence could dump 38-64cm of rain, with up to 90cm in some spots, forecasters said.
Communities in Florence's path could be without electricity for weeks due to downed power lines and flooded equipment, Federal Emergency Management Agency (FEMA) Administrator Brock Long said.