Hurricane Zeta was speeding toward storm-weary Louisiana with top winds of 155 km/h, strengthening to a Category 2 hurricane as it approached the coast.
New Orleans, where a pump system failure raised flood risks, was squarely in its path.
Workers closed one of the last floodgates surrounding the city as residents braced for the 27th named storm of a historically busy Atlantic hurricane season. The iconic streetcars shut down and City Hall closed until after the storm, Mayor LaToya Cantrell said.
Tropical storm warnings were issued as far away as the north Georgia mountains, highly unusual for the region. New Orleans has been in the warning areas of seven previous storms that veered east or west this season. Zeta was staying on course.
"I don't think we're going to be as lucky with this one," city emergency director Collin Arnold said.