Heavy rains and winds caused by Hurricane Matthew have hit Florida, where thousands of people are without power, officials say.
Matthew has been downgraded to a Category Three storm, with winds of up to 195 km/h (120 mph).
The storm could be the most powerful to strike northeast Florida in 118 years, the US National Hurricane Center said.
In Haiti, where Matthew devastated coastal villages and towns, the death toll has surpassed 300.
At 04:00 local time (08:00 GMT) Matthew was still off the Florida coast, centred about 45 miles (70km) east of Melbourne and was moving north-west at about 14mph (22km/h), the National Hurricane Center said.
Florida Governor Rick Scott there could be “catastrophic” damage if Matthew slammed directly into the state. He urged some 1.5 million people there to evacuate.
“If you’re reluctant to evacuate, just think of all the people this storm has already killed. You and your family could be among these numbers if you don’t take this seriously.”
More than 140,000 homes were without power, he added.
States of emergency were declared in four southern states, allowing the National Guard to be deployed. On Thursday afternoon, President Obama declared a state of emergency for Florida and South Carolina, allowing federal emergency teams to be sent.
Some two million people have been advised to evacuate across coastal areas of Florida, Georgia and South Carolina. North Carolina could also be affected as the storm moves north.