The boardwalk at the tourist town of Gulf Shores was virtually deserted except for John McCombs, who ventured out to see waves lapping at the sea wall at the public beach.
Within moments he was drenched and running for cover as a band of rain hit the wooden walkway.
“That's it. It's here,” he said, scurrying back across the street.
One question haunting locals is how much oil left over from the Gulf oil spill in 2010 might wind up on the beaches because of Isaac. Experts believe large tar mats lie submerged just off the coast, but no one knows where they are or how many might be in the Gulf.
Isaac was centered about 75 miles south-southeast of the mouth of the Mississippi River at midday and was moving northwest at 10 mph, according to the National Hurricane Center in Miami. It was 160 miles southeast of New Orleans.
Although Isaac's approach on the eve of the Katrina anniversary invited comparisons, the storm is nowhere near as powerful as Katrina was when it struck. Katrina at one point reached Category 5 status with winds of more than 157 mph, and made landfall as a Category 3 storm.
Still, forecasters at the National Hurricane Center warned that Isaac, especially if it strikes at high tide, could cause storm surges of up to 12 feet along the coasts of southeast Louisiana and Mississippi and up to 6 feet as far away as the Florida Panhandle.
Rain from the storm could total up to 14 inches, with some isolated areas getting as much as 20 inches, along the coast from southeast Louisiana to the extreme western end of the Florida Panhandle.
On Tuesday morning, there were few signs on New Orleans' famed Canal Street that a hurricane was imminent. A group of apparently intoxicated tourists asked 30-year-old Adrian Thomas to snap their photo as he scanned the headlines of The Times-Picayune in a newspaper box.
Thomas said he was waiting for his father to wire him money so he could leave for his hometown of Greenville, Miss., which is along the Mississippi River more than 200 miles from the coast. However, he said he might not make it out in time — and he was just fine with that.
“I believe it's going to be all right,” he said. “If I have to stay here and ride it out, I'll ride it out.”
In Mississippi, beachfront casinos were shutting down late Tuesday morning as a beach road flooded and residents hurried to shelters. Coastal residents Charlotte Timmons and Brenda Batey said they planned to stay put unless Isaac took a more menacing turn, believing it wouldn't cause the devastation of some past storms.
Since Katrina, people have a more cautious attitude toward tropical weather, perhaps so cautious that there's a danger of complacency setting in after near misses, Timmons said.
“It's like crying wolf,” said Timmons, a 63-year-old retired media manager. “If they make such a big deal and start moving people out (too soon) and then it fizzles, people might not leave the next time.”