Hurricane Michael is expected to strengthen on Tuesday in the Gulf of Mexico, taking aim at Florida, where residents were implored to get out of harm's way ahead of life-threatening waves, winds and rains.
Michael could be a Category 3 storm when it makes landfall, which is expected on Wednesday, becoming the most powerful storm to strike the area in at least a decade.
"For those considering evacuation, I can't stress strongly enough the importance of leaving as early as possible," Bay County Sheriff Tommy Ford said on Facebook. "Evacuation routes can quickly turn into traffic nightmares. Please evacuate now."
Michael was a Category 1 storm, with sustained winds of up to 150 km/ph, and gaining strength after it skirted Cuba's western tip, the National Hurricane Centre (NHC) said early on Tuesday.
Coastal storm surges of up to 3.7 metres are expected. As much as 30 cm of rain is forecast across Florida, Georgia and South Carolina.
The NHC warned that both could trigger deadly flooding and that residents within the hurricane warning zone should also "prepare for life-threatening winds."
Florida Governor Rick Scott declared a state of emergency in 35 counties.
About 1,250 National Guard soldiers were aiding the process and more than 4,000 troops placed on standby, Scott tweeted.
State offices, schools and universities were to close on Tuesday through the end of the week in affected areas.
Lines at petrol stations were growing as people prepared to leave. Those who planned to stay emptied grocery store shelves of water and other supplies throughout the day on Monday.
In Alabama, Governor Kay Ivey declared an emergency for the entire state on Monday, anticipating wind damage, heavy rains and power outages.
Torrential downpours and flash-flooding over the weekend caused 13 deaths in Central America after Michael formed off the coast of northern Honduras.
After striking Florida, Michael is forecast to move up the east coast on Wednesday and Thursday, plowing through the Carolinas, still recovering from Hurricane Florence last month.
