More than 500,000 people have lost power as Hurricane Isaac moves through south-east Louisiana, bringing torrential rain and flooding.
New Orleans is being hit with 80mph winds seven years to the day after the devastation caused by Hurricane Katrina.
Some residents are believed to be trapped, after a flood wall was breached.
Isaac, a massive storm spanning nearly 200 miles from its centre, zeroed in on New Orleans, turning streets famous for hosting celebrations at all hours into ghost boulevards. Evacuations were ordered in Mississippi's coastal counties and its 12 shorefront casinos were closed.
But hours before the Category 1 hurricane crossed land in Plaquemines Parish, there was little fear or panic. With New Orleans’ airport closed, tourists retreated to hotels and most denizens of a coastline that has witnessed countless hurricanes decided to ride out the storm.
“Isaac is the son of Abraham,” said Margaret Thomas, who was trapped for a week in her home in New Orleans’ Broadmoor neighbourhood by Katrina’s floodwaters, yet chose to stay put this time. “It’s a special name that means ’God will protect us’.”
Still, Isaac drew intense scrutiny because of its timing with the anniversary of Katrina and the first major speeches of the Republican National Convention in Tampa, Florida, already delayed and tempered by the storm.
“We don’t expect a Katrina-like event, but remember there are things about a Category 1 storm that can kill you,” New Orleans mayor Mitch Landrieu said, urging people to stay off any streets that may flood.
Other officials, chastened by memories and experience, advised caution. Tens of thousands of people were told to leave low-lying areas, including 700 patients of Louisiana nursing homes. At least one tornado spun off of Isaac in Alabama, but there were no immediate reports of damage or injuries.
Many residents along the Gulf Coast opted to ride it out in shelters or at home. Officials, while sounding alarm about the dangers of the powerful storm, decided not to call for the mass evacuations like those that preceded Katrina, which packed 135mph winds in 2005.
Isaac promises to test a New Orleans levee system bolstered after the catastrophic failures during Katrina. But in a city that has already weathered Hurricane Gustav in 2008, calm prevailed as residents sized up the threat.
“I feel safe,” said Pamela Young, who settled in to her home in the Lower 9th Ward – a neighbourhood devastated by Katrina – with her dog Princess and television, waiting for the storm. “Everybody’s talking, ’going, going’, but the thing is, when you go, there’s no telling what will happen. The storm isn’t going to just hit here.”
Ms Young, who lives in a new, two-story home built to replace the one destroyed by Katrina, said she wasn’t worried about the levees.
“If the wind isn’t too rough, I can stay right here,” she said. “If the water comes up, I can go upstairs.”
While Isaac remained far less powerful than Katrina, it posed similar political challenges, a reminder of how the storm seven years ago became a symbol of government ignorance and ineptitude.
President Barack Obama sought to demonstrate his ability to guide the nation through a natural disaster and the region’s Republican state officials reassured residents they were prepared, all the while readying for the coronation of Mitt Romney.
It was unclear what effect the storm might have on the festivities in Tampa, where the candidate’s wife Ann and New Jersey governor Chris Christie were the night’s featured speakers, after a day of delays.
There was already simmering political fallout from the storm. Republican governor Bobby Jindal, who cancelled his trip to the convention in Tampa, said the Obama administration’s disaster declaration fell short of the government help he had requested. Mr Jindal said he wanted a promise from the government to be reimbursed for storm preparation costs.
“We learned from past experiences, you can’t just wait. You’ve got to push the federal bureaucracy,” he said.
Federal Emergency Management Agency Administrator Craig Fugate said such requests would be addressed after the storm.
“We wanted to make sure direct federal assistance got out first,” he said.
Mr Obama promised that Americans would help each other recover, “no matter what this storm brings”.
“When disaster strikes, we’re not Democrats or Republicans first, we are Americans first,” Mr Obama said at a campaign rally at Iowa State University. “We’re one family. We help our neighbours in need.”