Ida was forecast to move well inland over portions of Louisiana and western Mississippi on Monday night. The National Weather Service issued a tornado watch for parts of Louisiana, including New Orleans, as well as parts of Florida, Mississippi and Alabama. Flooding was already underway in parts of Mississippi on Sunday morning.
New Orleans officials urged residents who did not evacuate to remain sheltered until the city can assess damage, likely Monday morning.
"Be calm in the midst of this storm," Mayor LaToya Cantrell said. "You have everything you need. We will get through this together."
City officials also expressed confidence in the flood protection system, which underwent a $14 billion upgrade after failing during Katrina. Hurricane Ida could dump up to 20 inches of rain on the city, Deputy City Administrator Officer Ramsey Green said.
However, a levee overtopped in Plaquemines Parish south of New Orleans, prompting officials to issue a warning.
New Orleans residents were asked to conserve water because of an electrical outage affecting the sewer system. Local utility Entergy New Orleans said it had provided extra generators and is working to find the cause of the outage, which did not affect the pumping system that clears the city of floodwaters, Green said.
Still, "it's an incredibly fragile system. That system can change at any point," Green warned.
Ida intensified so swiftly over three days that Cantrell said last week there was no time to organize a mandatory evacuation. She had, however, urged the city's 390,000 residents to leave voluntarily and warned those who stayed to prepare for long power outages.