NEW ORLEANS -- Hurricane Zeta slammed into the storm-weary Gulf Coast on Wednesday, pelting the New Orleans metro area with rain and howling winds that ripped apart buildings, knocked out power to thousands and threatened to push up to 9 feet of sea water inland in a region already pounded by multiple storms this year.

St. Bernard Parish President Guy McInnis said emergency workers were doing their best to respond to reports of people in distress after their roofs were blown off.

"Guys, we received the brunt of Zeta, and Zeta gave us a good punch," McInnis told WDSU-TV.

Roads were flooded near the coast, where forecasters said Zeta made landfall around Terrebone Bay near Cocodrie, an unincorporated fishing village at the end of a highway with few if any full-time residents and a marine laboratory where a building was inundated.

Streams of rainfall ran off roofs in New Orleans' famed French Quarter, signs outside bars and restaurants swayed back and forth in the wind and palm trees along Canal Street whipped furiously. A few trees were down, and one that fell across utility lines sparked a bright orange flash. Officials said a person was hospitalized with minor injuries after a structure collapsed, but further details weren't available.

More than 630,000 customers were without electricity in Louisiana, Mississippi and Alabama, including about 350,000 in metro New Orleans. More outages were feared overnight as the storm moves northeastward across the Deep South.

Zeta had top sustained winds of 110 mph (177 kph) as a Category 2 hurricane at landfall and is the 27th named storm of a historically busy Atlantic hurricane season -- with over a month left to go. It set a new record as the 11th named storm to make landfall in the continental U.S. in a single season, well beyond the nine storms that hit in 1916.

Zeta weakened to a Category 1 hurricane with winds of 90 mph (144 kph) as it moved into southern Mississippi few hours after landfall, but forecasters said it remained a life-threatening storm.

Tropical storm warnings were issued as far away as the north Georgia mountains, highly unusual for the region. Forecasters issued a string of tornado warnings for as far east as the Florida Panhandle.

New Orleans was in the warning areas of six previous storms that veered east or west this season. This time, Zeta stayed on course.

Louisiana Gov. John Bel Edwards said in a radio interview that boats broke loose and struck a bridge in Lafitte. He said blackouts were extensive, including 94% without power in Plaquemines Parish.

"The wind has caused extensive structural damages to businesses, to homes, to electrical infrastructure," Edwards said.

Officials had urged people to take precautions, and a business-as-usual atmosphere in the morning in New Orleans diminished as the storm neared and grew stronger. Traffic slowed, and restaurants and coffee shops shut down.

"This year, the storms have been coming back-to-back. They've been avoiding New Orleans but finally decided to come," cookie shop worker Curt Brumfield said as he stowed empty boxes in trash cans outside and others boarded up the windows ahead of the storm's arrival.

Winds picked up and water rose above the docks in Jean Lafitte, a small fishing town south of New Orleans that takes its name from a French pirate. Workers drove truckloads of sand to low-lying areas where thousands of sandbags were already stacked for previous storms.

"We're going to get a lot of water fast," said the mayor, Tim Kerner Jr. "I'm optimistic regarding the tidal surge because of the speed of the storm, but we're not going to take it for granted."

Zeta's wind, rain and storm surge reached more than 150 miles (241 kilometres) east of New Orleans. In Mississippi, streetlights swayed in Biloxi and the city of Pass Christian ordered all boats out of the harbour. Dauphin Island, Alabama, shut off water and sewer service in areas that typically are swamped in storms.

New Orleans officials announced that a turbine that generates power to the city's aging drainage pump system broke down Sunday, with no quick repair in sight. There was enough power to keep the pumps operating if needed, but little excess power to tap if other turbines fail, officials said.

Forecasts called for anywhere from 2 to 6 inches (5 to 15 centimetres) of rain to fall in the New Orleans area.

Before landfall, Zeta's top winds had risen to just shy of a major, Category 3 storm, according to the U.S. National Hurricane Center.

On Tuesday, Zeta raked across Mexico's Yucatan Peninsula, toppling trees and briefly cutting power to more than 300,000 people but causing no deaths.

It then regained strength over the Gulf of Mexico along a path slightly to the east of those of Hurricane Laura, which was blamed for at least 27 deaths in Louisiana in August, and Hurricane Delta, which exacerbated Laura's damage in the same area weeks later.

"I'm physically and mentally tired," a distraught Yolanda Lockett of Lake Charles, one of about 3,600 evacuees from Laura and Delta still sheltering, said outside her New Orleans hotel.

The deteriorating weather prompted early voting sites to close for hours in the western Florida Panhandle.

Hurricane warnings stretched from Morgan City, Louisiana, to the Alabama/Mississippi state line, including Lake Pontchartrain and metropolitan New Orleans.

Tropical storm warnings were issued for a large swath of the South, from Louisiana and Mississippi into Alabama and Georgia, including all of the Atlanta area, where winds could gust up to 55 mph (89 kph) early Thursday. Winds could be "especially severe" in the southern Appalachian Mountains, where flash flooding is possible, the hurricane centre said.

Large school systems in Alabama, Georgia and South Carolina planned to close Thursday or open late.

An average season sees six hurricanes and 12 named storms. This extraordinarily busy season has focused attention on climate change, which scientists say is causing wetter, stronger and more destructive storms.

After Hanna, Isaias, Laura, Sally and Delta, Zeta will tie a record set in 1886 and repeated in 1985 for six hurricanes smacking the continental U.S., according to Colorado State University hurricane researcher Phil Klotzbach.

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Plaisance reported from Laffite, Louisiana, and Santana from Shell Beach, Louisiana. Associated Press contributors include Gerald Herbert in New Orleans; Jay Reeves, in Birmingham, Alabama; Melinda Deslatte in Baton Rouge, Louisiana; Seth Borenstein in Kensington, Maryland; Jeff Martin in Marietta, Georgia; and Gabriel Alcocer in Cancun, Mexico.

Correction:

This story has been corrected. The New Orleans emergency director's surname is Arnold.