Hurricane Nate slammed into the southeastern tip of the US state of Louisiana on Saturday and headed toward Mississippi after leaving dozens dead and causing widespread flooding in Central America.

Officials urged residents to evacuate some vulnerable areas before the storm made landfall on Saturday evening, and residents scrambled to make last-minute preparations ahead of the third hurricane to hit the southern US in less than two months.

But US President Donald Trump said federal officials were ready for the fast-moving storm, urging residents of the states of Louisiana, Mississippi, Alabama and Florida on Twitter to "listen to your local authorities & be safe!"

Later Saturday, the eye of the storm was moving onshore the Mississippi coast the US National Hurricane Center (NHC) said in an update at 11:00 pm Saturday (0300 GMT Sunday), warning it would make its second landfall within one or two hours.

It predicted the storm would then pass over portions of several southern states through late Sunday.

The storm, a Category One hurricane on the five-point Saffir-Simpson scale, with winds swirling at 85 miles (140 kilometers) per hour, had slowed slightly from its earlier pace, heading north at about 20 miles per hour, the NHC said.

Heading north

The center warned that "the combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline."

Alabama Governor Kay Ivey tweeted that she had asked Trump to make a disaster declaration "to ensure we have all possible resources in place to respond to #HurricaneNate."

Trump earlier issued an emergency declaration for Louisiana and Mississippi allowing federal aid to be sent there to help mitigate the storm's impact.

New Orleans, which was ravaged in 2005 by Hurricane Katrina, leaving 1,800 people dead in the region, appears to have escaped Nate's wrath.

The mayor's office lifted a mandatory curfew that had been imposed as a safety measure, saying the hurricane warning for the city was no longer in effect.

Stocking up on supplies

Multiple shelters had been opened for evacuees from low-lying areas, and officials urged residents to finish preparations before evening, including stocking up on several days' supply of food and water.

"I lived through Katrina and I know what that was like," said Jackie Daigre, 69, who was buying groceries in preparation for the hurricane at a busy Walmart store, where the shelves of bottled water were picked almost completely bare.

Officials said the recent hurricanes, devastating as they were, actually helped with preparations for Nate, since emergency supplies and assets deployed for the earlier storms were still in place.

Still, the resources of the US Federal Emergency Management Agency (FEMA) have been stretched.

The New Orleans levee system has been considerably fortified since Katrina, but authorities warn that it has not completely eliminated flood risks.

Unlike Hurricane Harvey, which dumped record amounts of rain as it hovered over neighboring Texas for a week, fast-moving Nate was expected to pass through quickly along a northerly path.

Series of devastating hurricanes

Still, Louisiana Governor John Bel Edwards had warned that Nate could cause unexpected damage.

"Anyone in low-lying areas... we are urging them to prepare now," he said.

In neighboring Mississippi, lines formed at gas stations in areas along the potential path of the storm. Off the coast, some oil and gas rigs in the Gulf of Mexico have been evacuated.

With widespread electrical outages expected, New Orleans-area power provider Entergy prepositioned repair crews and warned that outages could last up to a week.

The United States is recovering from two major hurricanes: Harvey, which tore through Texas and then Louisiana in August, and Irma, which slammed Florida in September.

Another powerful storm, Hurricane Maria, ripped through the Caribbean in late September, devastating several islands, including Dominica and Puerto Rico, a US territory.

When Nate struck Central America on Thursday and Friday, at least 31 people were killed and others were still missing.

Intense rains forced thousands from their homes, uprooting trees, knocking out bridges and turning roads into rivers.