Eight people have died and 40,000 homes have been affected in the "historic flooding event" that has deluged Louisiana in recent days, Governor John Bel Edwards said at a press conference on Tuesday.
"It's unprecedented," he told reporters in Baton Rouge. "We understand that there are a lot of people who are suffering."
The governor said emergency crews had rescued more than 20,000 people and 1,000 pets and continued to search for more after a storm that broke historic records for 24-hour rainfall in multiple locations.
The area near Watson, Louisiana, was deluged with 31.39 inches of rain from Thursday to Monday morning, the highest total reported, according to the National Weather Service.
On Monday night, about 8,000 people stayed in shelters after floodwaters drove them from their homes, the governor said.
The flooding prompted U.S. President Barack Obama to issue a disaster declaration, with additional parishes given approval on Tuesday to be eligible for the federal assistance.