The first major hurricane threatening a direct hit on the US in more than 10 years has lashed Florida with heavy rain and winds after killing at least 339 people in Haiti on its destructive march north through the Caribbean.
Winds gusts of up to 100 kph and heavy downpours from Hurricane Matthew were reported in several coastal communities in Florida as the eye of the Category 4 hurricane tracked along the east coast of the state.
"We are just bracing and the winds are picking up," Daytona Beach Mayor Derrick Henry told CNN. "A great number of our residents have taken heed to our warnings and we are certainly concerned about those that have not."
More than 140,000 Florida households were without power, according to Governor Rick Scott. In West Palm Beach, once lit street lights and houses went dark and Interstate 95 was empty as the storm rolled through the community of 100,000 people.
Hurricane Matthew carried extremely dangerous winds of 215 kph as it pounded the northwestern part of the Bahamas en route to Florida's Atlantic coast earlier, the US National Hurricane Center said.
While Matthew's winds had dropped on Thursday night, it remained a Category 4 on the five-step Saffir-Simpson scale of hurricane intensity as it neared Florida, where it could either move inland or tear along the Atlantic coast through Friday night, the Miami-based centre said.
Few storms with winds as powerful as Matthew's have struck Florida, and the NHC warned of "potentially disastrous impacts."
The US National Weather Service said the storm could be the most powerful to strike northeast Florida in 118 years.
Hurricane conditions were expected in parts of Florida on Friday and a dangerous storm surge was expected to reach up to 3.4 metres along the Florida coast, Ed Rappaport, deputy director of the Miami-based NHC, said on CNN.
Some 339 people were killed in Haiti, local officials said, and thousands were displaced after the storm flattened homes, uprooted trees and inundated neighbourhoods earlier in the week. Four people were killed in the Dominican Republic.
Damage and potential casualties in the Bahamas were still unclear as the storm passed near the capital, Nassau, on Thursday and then out over the western end of Grand Bahama Island.
It was too soon to predict where Matthew might do the most damage in the United States, but the NHC's hurricane warning extended up the Atlantic coast from southern Florida through Georgia and into South Carolina.
More than 12 million people in the United States were under hurricane watches and warnings, according to the Weather Channel.