US officials say it is too late to flee from the path of Hurricane Michael – a category four storm – hours before it is due to hit the US mainland.
The storm is forecast to make landfall on Florida’s Gulf Coast, and is expected to be the largest storm to hit the region in 100 years.
Florida Governor Rick Scott warned citizens of “unimaginable devastation”.
At least 13 people reportedly died in Central America over the weekend as a result of storm rains and floods.
The storm has sustained winds of 145mph (230km/h) and is due to make landfall at about midday (16:00 GMT).
More than 370,000 people in Florida have been ordered to evacuate and move to higher ground, but officials estimate that far fewer have actually left.
“Do not leave your house,” Florida Governor Rick Scott said on Wednesday.
“The worst thing you can do now is leave,” he said, adding that those who do “put yourself and your family in danger”.
Federal Emergency Management Agency Director Brock Long was even more stark in his warning.
Those people “who stick around and experience storm surge unfortunately don’t usually live to tell about it,” he said, adding that they put first responders at risk as well.
Florida has declared a state of emergency, as have Alabama and Georgia.
Images on social media show scenes of flooding and wind damage.