The storm is expected to hit around midnight on Saturday after the National Hurricane Centre upgraded their tropical storm warning to a hurricane warning on Friday.
He said residents must evacuate by 12pm Saturday, when nearby floodgates will be closed.
After killing at least 22 people in Central America, the US regions of Alabama, Florida, Louisiana and Mississippi declared states of emergency as the storm heads towards the US Gulf Coast.
The Hurricane Centre said: “Residents in these areas should heed any evacuation instructions given by local officials.
“Life-threatening storm surge flooding is likely along portions of the northern Gulf Coast.”
Nate passed over Mexico at 21 miles per hour (mph) on Friday afternoon but is expected to strengthen as it hits the Louisiana coast.
New Orlean’s Mayor Mitch Landrieu told a press conference on Friday he had ordered the Sewerage and Water Board (SWB) to boost staffing at pump stations during the storm.
Officials promised the 120 pumps should be sufficient despite recent flooding.
He said officials are working “around the clock” to repair all pumps for the city’s drainage system.
However Humberto Suazo, chief financial officer of Link Restaurant Group said: “I don’t have full confidence in those pumps.
“We have had so many mixed messages.”
This will be the third hurricane to hit the US mainland in six weeks after Harvey and Irma devastated the east coast.
Memories from 2005’s Hurricane Katrina, when pumps failed to reduce flooding, are still fresh in New Orleans residents minds.
Steve Watson, owner of Kingpin bar and Midway Pizza said: “If we get 50 inches, there would be no way to pump that much water out of here.”
He added: “Even 10 to 15 inches of rain, some low-lying areas are going to be affected.”
Oil and gas companies have since pulled staff from offshore platforms.
The NHC’s update said: “On the forecast track, the centre of Nate will move across the northwestern Caribbean Sea today, and reach the eastern coast of the Yucatan peninsula early this evening.
“Nate will then move into the southern Gulf of Mexico tonight and approach the northern Gulf coast Saturday evening.”
Life-threatening flash floods and mudslides are forecast in parts of Nicaragua, Honduras, Costa Rica, Panama, and Belize through Friday night.