Houses have been totally submerged
Floodwaters have reached their highest level since the 1930s in the US city of Memphis, causing hundreds of people to leave their homes, reports Sky News.
Heavy rains and melting snow have swollen the Mississippi River, the largest river system in North America, and put pressure on the levees down river in New Orleans.
Residents fled to shelters after homes, businesses and schools were swamped by the floodwaters.
In one spot, the river widened to three miles (4.8 km), six times its normal width, while its flow speed had more than doubled to 12mph.
The soaking in Memphis, Tennessee, has mainly been isolated to low-lying neighbourhoods and it is believed the city's world-famous musical landmarks, Graceland and Beale Street, have been protected.
"I've never seen anything like it. I was born and raised here and it's pretty crazy to look at it," said Ashlee Omar, who works on Beale Street.
"It shouldn't get any worse than it currently is," said Elizabeth Burks, of the Army Corps of Engineers.
But to the south, residents in the Mississippi Delta, where there are no levees, are preparing for the worst as the waters continue to rise.
And the cost of the damage is expected to be huge with farmers losing their crops and thousands of properties affected.
Comparisons have been made to the Great Flood of 1927 which killed hundreds of people.
Engineers are concerned about the risk of levee failures which occurred during the devastation caused by Hurricane Katrina in 2005.
At the Louisiana State Penitentiary in Angola, home of the state's death row, officials started moving prisoners with medical problems to another prison as waters began to rise. The prisoners were moved in buses and vans under police escort.
The prison holds more than 5,000 inmates and is bordered on three sides by the Mississippi.
The prison has not flooded since 1927, though prisoners have been evacuated from time to time when high water threatened, most recently in 1997.