It has already battered Florida and Alabama with rain and storm surges, downing power lines, turning roads into rivers and leaving homes submerged.
Coastal communities are now taking stock of the damage.
One person was killed, and hundreds of thousands are without power.
Besides the fatality reported in Orange Beach, Alabama, one person is also missing from the small coastal city in southwest Alabama, according to Mayor Tony Kennon.
"It was an unbelievably freaky right turn of a storm that none of us ever expected," he told the Washington Post.