NEW ORLEANS - Nate has been downgraded from a hurricane to tropical storm, the National Hurricane Center said early on Sunday.

NHC said it was expected to quickly weaken as it moved farther inland across the deep south, Tennessee Valley and Central Appalachian Mountains.

Nate was about 135 mile (215 km) west-southwest of Montgomery Alabama with maximum sustained winds of 70 mph (110 kmh), the center said in a 3:30 am advisory.

Nate will turn toward the northeast with an increase in forward speed during the next couple of days, the center said.

Hurricane Nate slammed into the Mississippi coast on Sunday with destructive winds and torrential rains that flooded streets and highways throughout the region as the fast-moving Category 1 storm made landfall.

The fourth major storm to strike the United States in less than two months, Nate killed at least 30 people in Central America before entering the warm waters of the Gulf of Mexico and bearing down on the US South. It has also shut down most oil and gas production in the Gulf.

Nate comes on the heels of three other major storms, Harvey, Irma and Maria, which devastated Texas, Florida and Puerto Rico, respectively.

"The only thing you can do is prepare," said Gulfport, Mississippi, resident Emmett Bryant. "Here there's nothing really you can do when the storm comes unless you're going to leave. And I don't plan on leaving."

Nate made its initial landfall near the mouth of the Mississippi river on Saturday evening and then made a second landfall early on Sunday near Boloxi, Mississippi, where its 46,000 residents were warned that the highest storm surge could reach 3.35 to 3.66 meters.

The storm surge brought flood waters over Highway 90 and up to oceanside casinos in Biloxi, while flood waters swept over streets in communities across Mississippi and Alabama, according to reports on social media.

"We have a restaurant and one of our main bars open so they have been ok so far," said Chett Harrison, the general manager at the Golden Nugget hotel and casino in Biloxi where 300 guests were hunkered down.

"No one has tried to leave, thank goodness, because everything is flooded around us," he told a local CBS TV affiliate.

In Hancock County, Mississippi, northeast of New Orleans, rain and wind were gaining intensity and many streets were washing over. Conditions were likely to worsen in the next few hours, said Brian Adam, director of emergency management for the county.

The county evacuated people from low-lying areas and imposed a curfew.

On Saturday states of emergency were declared in Louisiana, Mississippi and Alabama, as well as in more than two dozen Florida counties.

In Alabama, Governor Kay Ivey urged residents in areas facing heavy winds and storm surges to take precautions.

Some 5,000 people in southern Alabama were without power due to Nate, Alabama Power said.

New Orleans Mayor Mitch Landrieu lifted a curfew in the city on Saturday evening that was originally scheduled to last until Sunday morning. He said in a statement on social media, however, that there was still a serious threat of storm surge outside levee areas.

Plaquemines Parish, a low-lying area south of New Orleans, evacuated some 240 residents who were not protected by its levee system as the storm approached.

"While it appears we're being spared ... our hearts go out to Mississippi," said Amos Cormier, president of the parish.

Major shipping ports across the central US Gulf Coast were closed to inbound and outbound traffic on Saturday.

Reuters