‘Historic’ Louisiana Flooding Affects 40,000 Homes, Governor Says

About 40,000 homes in southeastern Louisiana have been affected by days of devastating flooding, which Gov. John Bel Edwards today described as "unprecedented" and "historic."

At least eight people have died, he said, adding that authorities remain in emergency search mode in many parishes.

Edwards said that over 20,000 people have been rescued and about 8,000 were in shelters Monday night.

President Obama declared a federal emergency in the state on Sunday.

Of the 54,000 homes in southeastern Louisiana's Livingston Parish, in the Baton Rouge area, authorities estimate that 80 percent of residents will face a total loss when they return home, parish Sheriff Jason Ard told ABC News.

In 24 hours, 21 inches of rain fell in Livingston Parish, just under the 24-hour state record of 22 inches, set in 1962.