Coastal Alabama is under a mandatory evacuation order as Isaac churns through the Gulf of Mexico.
Gov. Robert Bentley ordered residents of southern Baldwin and Mobile counties to begin evacuating starting 8 a.m. Monday, and both counties are under a hurricane warning.
A state of emergency covers the entire state of Alabama, and the governor has told the National Guard to be on standby.
More than a foot of rain could fall in coastal areas, forecasters warned.
The deluge was expected to begin Monday night, and could total 8-12 inches by Thursday, the National Weather Service said in a statement early Monday. Local areas near the coast could see 15 inches of rain, forecasters said.
Beach hotels in Gulf Shores and Orange Beach are making plans to close, and public schools in the two coastal counties are closed at least through Wednesday.
Store shelves are emptying of batteries and gasoline cans, and many people spent the weekend boarding up windows and doors along the coast.
Forecasters said Isaac will bring the threat of flooding and tornadoes to the southwest corner of Georgia.
The National Weather Service said 5 to 7 inches of rain is possible in parts of southwest Georgia, with the potential for even higher amounts.
There’s also a possibility of tornadoes in a region of southwest Georgia that includes Albany and areas to the south and west of that city.
The storm will likely make landfall on the northern Gulf Coast late Tuesday, so the location was still far from certain, authorities said.