Tropical Storm Nate is now Hurricane Nate as it moves into the southern Gulf of Mexico.

The storm's maximum sustained winds increased to 80 mph around 4 a.m. the National Hurricane Center said.

The center of Nate will move across the Gulf of Mexico overnight and on Saturday and is expected to make landfall along the central Gulf coast either Saturday evening or Saturday night. 

A hurricane warning remained in place for Grand Isle, Louisiana to the Alabama-Florida border and the New Orleans metropolitan area and Lake Ponchartrain.

Nate is expected to bring between three to six inches of rain east of the Mississippi River from the central Gulf Coast into the Deep South, eastern Tennessee Valley and southern Appalachians, with some areas seeing a maximum of 10 inches. Isolated tornadoes are also possible beginning Saturday afternoon over parts of the central Gulf Coast region. 

A storm surge warning is also in effect for Morgan City, Louisiana to the Okaloosa/Walton County Line in Florida and the northern and western shores of Lake Ponchartrain, with water expected to reach between four to six feet from Morgan City to the mouth of the Mississippi River and five to eight feet from the mouth of the Mississippi River to the Alabama-Florida border. 

The NHC said aircraft data shows Nate as an asymmetric storm with most of the winds located on the eastern side of its circulation. This pattern should continue until Nate makes landfall, meaning locations east of where Nate makes landfall are expected to receive significantly stronger winds than locations to the west of the center.

Forecasters suggested the possibility that Nate may not gain further strength before it makes landfall Saturday along the Gulf Coast, but have not ruled out rapid intensification over the next 24 hours. 

Louisiana and Mississippi officials declared states of emergency ahead of the storm, and the towns of Jean Lafitte and Grand Isle have ordered mandatory evacuations. The city of Gretna and New Orleans have instituted curfews ahead of the storm.

Gov. John Bel Edwards has also mobilized 1,300 National Guard troops, with 15 headed to New Orleans to monitor the fragile pumping system.

Edwards urged residents to ready for rainfall, storm surge and severe winds — and to be where they intend to hunker down by "dark on Saturday."

Edwards said Nate is forecast to move quickly, rather than stall and drop tremendous amounts of rain on the state. State officials hope that means New Orleans won't run into problems with its pumps being able to handle the water.

Edwards warned, however, against underestimating the storm.