Up to 5,000 Mississippi residents may be forced to evacuate, authorities said. The river has washed away crops and forced people to leave their homes.
The flooding has badly affected Memphis and other cities further upstream, news agencies reported.
In Arkansas flooding along the White River forced officials to close Interstate 40, one of the busiest highways in the state.
Louisiana’s St Martin Parish gave jail inmates the task of filling sandbags to protect homes on ground that could be flooded.
Officials have said the flooding could take weeks to recede.
The National Weather Service said, that the flood crest has passed Memphis and is expected to move downstream toward New Orleans within the next three weeks.
The flood is the result of a wet spring and huge snow melt from an unusually stormy winter.
Thunderstorms are also expected on Thursday night into Friday, which could bring another inch of rain into the area.
In Mississippi, 16 casinos remain closed along the river and two more in Vicksburg.
A 300-animal shelter in Natchez began accepting evacuees’ pets on Wednesday.
The 2011 flood has been breaking records set during historic floods in 1927 and 1937.