Hurricane Florence, which is nearing the US East Coast, could kill "a lot of people", officials warn.
The Federal Emergency Management Agency (Fema) says storm surges could bring catastrophic flooding to inland areas.
Nearly 1.7m people along the coastlines of North Carolina, South Carolina and Virginia have been ordered to evacuate.
Strong winds and heavy rains have already begun lashing North Carolina's coastline, leading to some early flooding.
Some 11,000 power outages had already been reported in the state. Reuters news agency reports.
Florence was 155 miles (250km) east of Myrtle Beach in South Carolina at 17:00 EDT (21:00 GMT), and is projected to make landfall on Friday at 08:00 local time.
It was downgraded to a category two storm with 105mph (165km/h) winds, and the US National Hurricane Center (NHC) said it does not expect much change in the strength before the eye of Florence makes landfall.