The US city of New Orleans has lost power, with only generators working, as Hurricane Ida batters Louisiana.
The storm brought 150mph (240km/h) winds when it made landfall and those people who did not flee have been advised to shelter in place.
One person was killed when a tree fell on their home in Ascension Parish, in the Baton Rouge area.
Ida will test New Orleans’ flood defences, strengthened after Hurricane Katrina killed 1,800 people in 2005.
President Joe Biden said Ida would be “life-threatening”, with immense devastation likely beyond the coasts.
In pictures: Hurricane Ida lashes Gulf Coast
Over one million homes in Louisiana are without power, and Mr Biden said it could take weeks to restore supplies.
The president has declared a major disaster in the state, releasing extra funds for rescue and recovery efforts.
Ida gathered strength over the warm waters of the Gulf of Mexico during the weekend.
It made landfall on Sunday south of New Orleans as a category four hurricane – meaning it would cause severe damage to buildings, trees and power lines. As it moves inland, Ida’s winds have dropped to 95mph (153km/h), meaning it is now a category one storm.
In some places the storm surge could be as high as 16ft (4.8m), potentially submerging parts of the low-lying coastline.