Nate spawned widespread flooding and left dozens of people dead in Central America, the latest in a series of deadly storms to hammer Caribbean islands, Mexico and the southeastern US in this exceptionally busy hurricane season.
But US President Donald Trump said federal officials were prepared for the fast-moving storm. He urged residents of the states of Louisiana, Mississippi, Alabama and Florida on Twitter to "listen to your local authorities & be safe!"
As a weary and sodden region prepared for its third hurricane in two months -- filling sandbags, stocking up on essential supplies or packing cars to flee -- New Orleans, which was ravaged by deadly Hurricane Katrina in 2005, and other cities on the coast were under a hurricane warning.
Nate's center "will pass near or over the mouth of the Mississippi River during the next few hours, then make landfall along the coasts of southeastern Louisiana or Mississippi tonight," the US National Hurricane Center (NHC) said at 4:00 pm (2100 GMT).
'In the fight'
The storm, a Category One hurricane on the five-level Saffir-Simpson scale, with winds swirling at around 90 miles (150 kilometers) per hour, could strengthen into a Category Two before making landfall, the NHC said.
"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," the NHC warned.
New Orleans Mayor Mitch Landrieu told a news conference that the impact of the hurricane was already being felt.
"We're in the fight now. The storm is on us," Landrieu said.
"It's going to hit you hard. It's going to hit you fast."
Alabama Governor Kay Ivey tweeted that she had asked Trump for a presidential declaration of emergency, "to ensure we have all possible resources in place to respond to #HurricaneNate."
Trump earlier issued an emergency declaration allowing federal aid to be sent to help mitigate the storm's impact.
New Orleans issued a mandatory curfew for Saturday from 6:00 pm, and mandatory and voluntary evacuation orders were issued for certain low-lying areas.
Stocking up on supplies
Multiple shelters were opened for evacuees, and officials urged residents to finish preparations before evening, including stocking up on several days' supply of food and water.
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.
National Guardsmen were prepared to ride out the storm in the city's huge Superdome arena, ready to respond once Nate passes over, the nola.com news website reported.
The city's levee system has been considerably fortified since Katrina claimed some 1,800 lives in the region, 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.
Still, Louisiana Governor John Bel Edwards warned that Nate could cause unexpected damage.
Power outages expected
"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 to go to work once the hurricane passes, 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.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)