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.
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"I don't think we're going to be as lucky with this one," city emergency director Collin Arnold said.
Zeta had been predicted to hit as a relatively weak Category 1 hurricane, but Louisiana residents awoke to updated forecasts predicting a Category 2 at landfall.
"The good news for us - and look, you take good news where you can find it – the storm's forward speed is 17 mph. That's projected to increase, and so it's going to get in and out of the area relatively quickly, and then we're going to be able to assess the damage more quickly," Governor John Bel Edwards told the Weather Channel.
Officials urged people to take precautions and prepare to shelter in place, but there were few signs of concern in New Orleans. It was business as usual in the French Quarter. "This one is moving fast and I don't think it's going to do much," said Kelly Ann, a visitor from St Petersburg, Florida, as she strolled Decatur Street.
The winds were picking up and water was rising above the docks in Jean Lafitte, a small fishing town south of New Orleans that takes its name from a French pirate. Workers drove truckloads of sand to low-lying areas where thousands of sandbags were already stacked before previous storms.