Tropical storm Isaac was on the verge of becoming a full-blown hurricane as it rolled over the Gulf of Mexico toward Louisiana.
Householders in four states left boarded-up homes for inland shelter and New Orleans waited behind flood-defence levees strengthened after the devastating Katrina struck exactly seven years ago.
Forecasters predicted the tropical storm would power up to hurricane strength, which starts at winds of 74 mph later and become at least a Category 1 hurricane by the time it reached the coast of Louisiana.
The focus has been on New Orleans as the massive, slow-moving storm takes dead aim at the city, but the impact will be felt well beyond the city limits, especially in expected storm surges of up to 12 feet in Louisiana, Mississippi, Alabama and the Florida Panhandle. The storm’s winds could be felt more than 200 miles from its centre.
The storm has churned into the middle of the tight US presidential election, with Republicans this week meeting nearby in Florida to nominate Mitt Romney to challenge president Barack Obama.
Mr Obama, mindful of how his administration’s response to the storm could be judged, spoke about Isaac from the White House before departing on a three-state campaign trip.
“Now is not the time to tempt fate,” he said. “You need to take this seriously.”
Although Isaac’s approach on the eve of the Katrina anniversary invited obvious comparisons, the storm is nowhere near as powerful as Katrina was when it struck on August 29, 2005. Katrina at one point reached Category 5 status, with winds of more than 157 mph and made landfall as a Category 3 storm.
Mayor Mitch Landrieu did not activate a mandatory evacuation for Isaac. Instead, officials urged residents to make do with the supplies they had.
Federal officials said the updated levees around New Orleans are equipped to handle storms stronger than Isaac.
But anxiety was high, especially in the city’s Lower 9th Ward, wiped out by Katrina after floodwalls burst and let the waters rush in.
“I don’t really trust the levees,” said Robert Washington, who planned to evacuate along with his wife and five children. “I don’t want to take that chance. I saw how it looked after Katrina back here.”
His neighbourhood, just a few blocks from where the floodwall protecting the Lower 9th Ward broke open, remains largely empty.
Forecasters at the National Hurricane Centre warned that Isaac, especially if it strikes at high tide, could cause storm surges of up to 12 feet along the coasts of Louisiana and Mississippi and up to 6 feet as far away as the Florida Panhandle.
States of emergency were in effect in Louisiana, Mississippi, Alabama and Florida.
Isaac left 24 dead in Haiti and the Dominican Republic but left little damage in the Florida Keys as it blew past. It also delayed the planned start of the Republican National Convention.
The approaching storm was already deeply woven into political concerns beyond the Republican convention. The slow response to Katrina, which killed 1,800 and left New Orleans in chaos, led to severe criticism of then-President George W. Bush’s Republican administration. This time, both Mr Obama and Mr Romney are cautious about the impressions made.