Almost 800 rescued in St. John the Baptist Parish after Hurricane Ida

Entergy, Louisiana's major electricity provider, is reporting more than 130,000 customers without power in East Baton Rouge Parish as Hurricane Ida pummels the area, according to Baton Rouge Mayor Sharon Weston Broome.

DEMCO, the largest electric cooperative in Louisiana, is also reporting over 7,000 outages in East Baton Rouge Parish, which is home to some 440,000 people. Meanwhile, at least 20 roads are closed throughout Louisiana's most populous parish due to fallen trees and six structures have been heavily damaged, Broome said in a video message posted on Twitter early Monday.

"There could be more trees down overnight and more damage to structures," the mayor warned. "We need everyone to remain vigilant, to stay in your home because we want you and your family to stay safe."

Broome has issued a curfew for East Baton Rouge Parish from Sunday at 8 p.m. ET to Monday at 7 a.m. CT. She urged residents to "stay in as long as possible" to allow first responders, local officials and utility company workers to assess the damage and restore power to the area.

"The truth of the matter is, restoring power could take some time," Broome admitted.

The mayor of Lafitte, Louisiana, is pleading for help Sunday night, saying the town needs help with water rescues. He told ABC News affiliate WGNO that 200 people were stranded.

"Never seen one like this," Mayor Tim Kerner Jr. told the station. "Worst storm in our history."

He said the storm waters are over the levees, have destroyed and school and has put people in "imminent" danger.

Ida has weakened to a Category 2 hurricane as it batters Louisiana. Six to 12 inches of rain has fallen in some parts of the state and another 4 to 6 inches is possible.

President Joe Biden has approved Louisiana Gov. John Bel Edward's request for a Presidential Major Disaster Declaration.

Ida is expected to weaken to a tropical storm Monday as it slowly moves into southwestern Mississippi with heavy rain, strong winds and flash flooding. Ida will continue to bring heavy rain through Monday across southeast Louisiana, coastal Mississippi and southwestern Alabama.

Through Wednesday, as Ida moves inland, considerable flooding is possible in parts of the lower Mississippi Valley, Tennessee Valley, upper Ohio Valley, Central Appalachians and Mid-Atlantic.

-ABC News' Melissa Griffin

Louisiana's Ochsner Health hospital system will evacuate 66 patients from two hospitals due to damaged roofs and windows, hospital officials said.

-ABC News' Matt Foster