Hurricane Matthew weakened to a Category 3 storm overnight on Friday, but the National Hurricane Center (NHC) insisted that it remained "extremely dangerous" as it moved closer to the east coast of Florida.
It came after President Barack Obama declared a state of emergency for Florida, Georgia and South Carolina on Thursday, and Florida Gov. Rick Scott, begged residents to flee from the predicted landfall.
Hurricane Matthew packed gusts of 100 miles per hour (160 kph) as it tracked north-northwest along Florida's east coast, the National Hurricane Center said in an advisory. The storm's eye was 25 miles (40 km) east of Cape Canaveral, home to the nation's chief space launch site.
The NHC added that the center of the hurricane was expected to move "near or over" the East Coast of the Florida peninsula overnight on Friday and reach the coasts of Georgia and South Carolina on Saturday. The maximum sustained winds are forecast to be 120 miles an hour.
Matthew's winds had dropped on Thursday night and into Friday morning, downgrading it to a Category 3 on the five-step Saffir-Simpson scale of hurricane intensity, where it could either plow inland or tear along the Atlantic coast through Friday night, the Miami-based center said.
Few storms with winds as powerful as Matthew's have struck Florida, and the NHC warned of "potentially disastrous impacts."
The U.S. National Weather Service said the storm could be the most powerful to strike northeast Florida in 118 years.
Around 1.5 million people have fled Atlantic coastal areas as the storm nears land.
About 300,000 Florida households were without power, local media reported. 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.
North Carolina Gov. Pat McCrory declared a state of emergency in all 100 counties in the state.
The declaration allows the Department of Homeland Security and Federal Emergency Management Agency to aid state and local responses to Matthew, which could cause tens of billions of dollars of damage to coastal areas.
Obama committed to providing necessary federal resources to help states respond to the hurricane in separate phone calls with the governors of Georgia, South Carolina, North Carolina and Florida. The president also asked those in affected areas to follow the guidance of emergency response officials.