Anxious Florida residents raided grocery store shelves and North Carolina called for the evacuation of three barrier islands as Hurricane Matthew - the most powerful Atlantic storm in about a decade - threatened to rake a large swath of the East Coast in the coming days.
The storm roared across the Caribbean today, slamming into the western part of Haiti.
While it's 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 was in place for parts of Florida, which was already seeing rain bands from the storm.
Simone Corrado and her husband tried to buy water in their hometown of Davie, about 20 minutes from Miami Beach, and mostly found empty shelves.
"I got scared because all that was left at Publix was just the pricey water," Corrado said. "They really put the fear into you here. On the television screen every few minutes is the 'beep, beep, beep' storm alert."They were worried the roof of their garden-style apartment would leak during heavy rain.
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 said.
At least seven people have died from Matthew's march through the Caribbean. The storm was headed north over the Bahamas and expected to brush the Florida coast.
A tropical storm watch was issued from Seven Mile Bridge in the Florida Keys to Deerfield Beach, north of Fort Lauderdale. A hurricane watch is in place further north.
"We are preparing for the worst, hoping for the best and not taking any chances," Scott said.
The Governor urged residents along the Interstate 95 corridor to start making preparations, which include having at least a three-day supply of water, food and medicine. He also asked residents to comply with any evacuation orders from local officials as the week progresses."
Federal officials have been deployed to state emergency operations centres in Florida, Georgia, South Carolina and North Carolina and relief supplies have been prepositioned 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. He said he doesn't want other crops ruined, so restrictions on truck weights and hours of service would be lifted under the emergency declaration to allow farmers to take their harvest to market.
At Cape Lookout National Seashore in North Carolina, superintendent Patrick Kenney said more than 100 trucks were being taken off the island and about 45 cabins were being cleared.
Ferry operators told Kenney it will take two days to evacuate everyone, meaning the islands should be empty sometime tomorrow.