Hurricane Nate is expected to strengthen and make landfall, threatening the US central Gulf Coast with strong winds and storm surges after killing at least 25 people in Central America.
Nate, a Category 1 hurricane, the weakest on a five-category scale used by meteorologists, was churning toward the central Gulf of Mexico as New Orleans evacuated some residents from areas outside its levee system.
"Nate is at our doorstep or will be soon," New Orleans Mayor Mitch Landrieu said on Saturday.
The greatest threat from this particular storm is not rain, but strong winds and storm surge, Landrieu said. The winds could cause significant power outages, and storm surges are projected to be 1.8 to 2.7 metres high, he added.
"We have been through this many, many times. There is no need to panic," Landrieu told a news conference.
The storm brushed by Mexico's Yucatan peninsula, home to beach resorts such as Cancun and Playa del Carmen, as it headed north, the US National Hurricane Center in Miami said.
Nate packed maximum sustained winds of 130km/h and was about 675km south-southeast of the Mississippi river on Saturday as it was expected to strengthen, the NHC said.
In the US, a state of emergency was declared for 29 Florida counties and states near Nate's path - Alabama, Louisiana and Mississippi - as well as the city of New Orleans, which was devastated by Hurricane Katrina in 2005.
The NHC issued a hurricane watch from Grand Isle, Louisiana to the Alabama-Florida border.
The storm doused Central America with heavy rains on Thursday, killing at least 12 people in Nicaragua, nine in Costa Rica, two in Honduras and two in El Salvador, local authorities said.
Thousands were forced to evacuate their homes and Costa Rica's government declared a state of emergency.
