Obama has declared a state of emergency in Florida as a result of the threat of fiery storm, Hurricane Matthew approaching the city.
The action authorizes the Department of Homeland Security and the Federal Emergency Management Agency to coordinate disaster relief efforts necessitated by the storm, a Category 4 hurricane packing winds of 140 mph (220 kph).
In Florida, fuel stations posted "out of gas" signs after cars waited in long lines to fill up. At a Subco gas station in Orlando, the gas pumps ran dry on Wednesday afternoon.
The shop was a stopping off point for coastal residents seeking shelter inland from the coast. Among them was Jonas Sylvan, 44, of Melbourne, Florida, who planned to hole up in a hotel with his wife, two daughters and dog. "We're just trying to get away from the coast," he said. "It's safer here."
Bumper-to-bumper traffic extended for more than 10 miles (16 km) on the main highway leading west to Orlando from the coast.
In the central Florida coastal city of Jupiter, people scrambled to make preparations.
"Our house is wood construction, so who knows what will happen," said Libby Valentine, 75, of Jupiter. "The whole idea is to stay safe and hope you have the grace to deal with the aftermath because you might not have a house."
Most stores were closed or planning to do so soon. A line of two dozen cars snaked out of a Marathon gas station and tied up traffic on a nearby road. Next door, the windows of a Sabor Latino Supermarket were covered with plywood and a hand-written sign said it closed at noon.