Anxious Floridians are on high alert and North Carolina has called for the evacuation of three barrier islands as Hurricane Matthew threatens a large swathe of the US east coast.
The hurricane is the most powerful Atlantic storm in a decade, and has already roared across the Caribbean and slammed into the south-western tip of Haiti.
Winds reaching 145mph tore off roofs in the poor and largely rural area of the island, uprooting trees and leaving rivers bloated and choked with debris.
At least seven deaths have been blamed on the storm during its week-long march across the Caribbean. Damage in Haiti appeared to be widespread, but because of poor communications, blocked roads and washed-out bridges, the full extent of the damage or the number of casualties is not immediately clear.
While it is too soon to know if it will make a direct hit on Florida or somewhere else along the US coast, Matthew is expected to create dangerous conditions.
A hurricane watch is in place for parts of Florida, which is already experiencing bands of rain from the storm.
Florida governor Rick Scott met emergency officials along the coast, starting out in the Keys and travelling north. At a news conference in Daytona Beach, he noted that the storm's predicted path can change quickly.
"We can rebuild your home, we can rebuild your business. We can't rebuild your life," Scott warned.
"We are preparing for the worst, hoping for the best and not taking any chances," Scott said, as he visited emergency management officials in the Florida Keys.
The governor urged residents along the Interstate 95 motorway corridor to start making preparations, which include having at least a three-day supply of water, food and medicine.
Matthew briefly reached the top classification, Category 5, becoming the strongest hurricane in the region since Felix in 2007.
Federal officials have been deployed to state emergency operations centres in Florida, Georgia, South Carolina and North Carolina and relief supplies have been sought in the region.
North Carolina governor Pat McCrory declared a state of emergency, in part to immediately help farmers clear their fields of crops already affected by heavy rain over the last two weeks.