Homeowners have sandbagged their doors and tourists trying to get out of town have jammed the airport as Tropical Storm Barry began rolling in, threatening an epic drenching that could test how well New Orleans has strengthened its flood protections in the 14 years since Hurricane Katrina.
With the storm expected to blow ashore early Saturday near Morgan City as the first hurricane of the season, authorities rushed to close floodgates and raise the barriers around the New Orleans metropolitan area of 1.3 million people for fear of disastrous flooding.
The storm was expected to inflict the most damage on Louisiana and parts of Mississippi, with wind and rain affecting more than 3 million people.
About 3,000 National Guard troops, along with other rescue crews, were posted around Louisiana with boats, high-water vehicles and helicopters. Drinking water was lined up, and utility crews with bucket trucks moved into position.
"This is happening. ... Your preparedness window is shrinking," National Hurricane Centre Director Ken Graham warned. He added: "It's powerful. It's strengthening. And water is going to be a big issue."
While 10,000 people or more in exposed, low-lying areas along the Gulf Coast were told to leave, no evacuations were ordered in New Orleans, where officials instead urged residents to "shelter in place" starting at 8 pm
"My concerns are just hoping it's not going to be another Katrina," said Donald Wells, a restaurant cook in New Orleans.
Forecasters said slow-moving Barry could unload 25 to 50 centimetres of rain through Sunday across a swath of Louisiana that includes New Orleans and Baton Rouge, as well as southwestern Mississippi, with pockets in Louisiana getting 63 centimetres.
The storm's leading edges lashed the state with bands of rain for most of the day, and some coastal roads were already underwater.
Barry was expected to arrive as a weak hurricane, just barely over the 74 mph (119 kph) wind speed threshold. But authorities warned people not to be fooled.
"Nobody should take this storm lightly just because it's supposed to be a Category 1 when it makes landfall," Gov. John Bel Edwards said. "The real danger in this storm was never about the wind anyway. It's always been about the rain."
Authorities took unprecedented precautions: The governor said it was the first time all floodgates were sealed in the New Orleans-area Hurricane Risk Reduction System. Still, he said he didn't expect the river to spill over the levees.
Workers also shored up and raised the levee system in places with beams, sheet metal and other barriers.
Barry's downpours could prove to be a severe test of the improvements made to New Orleans' flood defences since Katrina devastated the city in 2005. The Mississippi River is already running abnormally high because of heavy spring rains and snowmelt upstream, and the ground around New Orleans is soggy because of a 20-centimetre torrent earlier this week.