New Orleans (AFP) - Louisiana braced Sunday for Hurricane Ida, a powerful Category 4 storm on course to slam into New Orleans 16 years to the day after deadly Hurricane Katrina devastated the southern US city.

Showers and strong wind swept New Orleans' deserted streets Sunday morning, buffeting boarded-up windows at businesses and homes surrounded by sandbags.

State Governor John Bel Edwards said Ida, which has gathered force on its approach through the warm waters of the Gulf, could be the most powerful storm to hit the state since 1850.

By midday Sunday, storm surges were already flooding the town of Grand Isle, on a barrier island south of New Orleans, CNN reported.

Amid urgent warnings of catastrophic damage, most residents have heeded authorities' instructions to flee. Scores of people packed bumper-to-bumper roads leading out of New Orleans in the days preceding Ida's arrival.

The hurricane, packing maximum sustained winds of 150 miles (240 kilometers) per hour was expected to make landfall along the southeastern Louisiana coast "within the next few hours," the National Hurricane Center reported in its 1500 GMT advisory.

In one neighborhood in eastern New Orleans, a few residents were still completing last-minute preparations.

"I'm not sure if I'm prepared," said Charles Fields, who was still bringing his garden furniture indoors, "but we just have to ride it."

The 60-year-old, who in 2005 saw Hurricane Katrina flood his house with 11 feet (3.3 meters) of water, added that "we'll see how it holds up."

'Very Serious Test'

Governor Edwards warned on Sunday that Ida would be "a very serious test for our levee systems."

He told CNN that hundreds of thousands of residents were believed to have evacuated.

The storm "presents some very challenging difficulties for us, with the hospitals being so full of Covid patients," he said.

The southern state, with a low rate of vaccinations, has been among the hardest hit by the pandemic, severely stressing hospitals. Hospitalizations, at 2,700 on Saturday, are near their pandemic high.

The memory of Katrina, which made landfall on August 29, 2005, has not begun to fade in Louisiana, where it caused some 1,800 deaths and billions of dollars in damage.

"It's very painful to think about another powerful storm like Hurricane Ida making landfall on that anniversary," Edwards had previously said.

Rainfall of 10 to 18 inches (25 to 46 centimeters) is expected in parts of southern Louisiana through Monday, with up to 24 inches in some areas.

Ida And Delta Variant

The White House said Sunday that federal agencies had deployed more than 2,000 emergency workers to the region -- including 13 urban search-and-rescue teams -- along with food and water supplies and electric generators. Extensive and long-lasting power outages are expected.

Local authorities, the Red Cross and other organizations have prepared dozens of shelters with room for at least 16,000 people, the White House added. Plans to cope with the hurricane -- and plans for the shelters -- have been complicated by Covid-19. President Joe Biden, who has declared a state of emergency for Louisiana, on Saturday urged anyone in community shelters to wear masks and maintain distance.

Scientists have warned of a rise in cyclone activity as the ocean surface warms due to climate change, posing an increasing threat to the world's coastal communities.