Hurricane Michael was upgraded to an "extremely dangerous" category 4 storm on Wednesday, hours before it is due to make landfall in the US state of Florida, where it could blow ashore as the strongest storm to hit the country this year.
The hurricane was expected to make landfall in the afternoon, causing "potentially catastrophic" damage to the region, CNN reported.
Michael, packing winds of 230 kph (145 mph), was moving north at 20 kph (13 mph) towards the Florida Panhandle, the National Hurricane Centre said in public advisory.
More than 370,000 people in the state were ordered to evacuate and move to higher ground. Florida, Alabama and Georgia declared a state of emergency.
Forecasters said the storm's torrential rains were likely to cause widespread flooding, cutting off low-lying areas on the coast.
At least 13 people reportedly died in Central America over the weekend as a result of storm drains and floods.
State officials issued mandatory or voluntary evacuation orders in at least 22 counties on the Florida Gulf Coast.
Scott extended a state of emergency to 35 counties and activated 2,500 National Guardsmen.
President Donald Trump approved a pre-landfall emergency declaration to provide federal money and help in Florida.
Heavy rains were forecast for the Carolinas, which were drenched by Hurricane Florence in September.
North Carolina Governor Roy Cooper told residents: "I know people are fatigued from Florence, but don't let this storm catch you with your guard down."
Georgia Governor Nathan Deal declared an emergency for 92 counties, while Alabama Governor Kay Ivey issued a statewide state of emergency, saying on Twitter it was "in anticipation of widespread power outages, wind damage and debris produced by high winds and heavy rain associated with Hurricane Michael".
(With inputs from agencies.)