An official state of emergency has been declared in 13 states in total, enabling the federal government to release relief money to care for the evacuees. States across America are taking in refugees, or making plans to do so in the coming days.

In addition the Red Cross is caring for more than 135,000 people at 470 shelters in 12 states.

The exodus has overwhelmed some areas. Hotel rooms are booked up for miles around, and state authorities have taken over stadiums, military barracks and other venues to provide shelter.

Texas has faced the largest volume of refugees, currently taking in more than 239,000. The state has been able to house thousands in large venues in the city of Houston but is also flying some evacuees to other states and. There are plans to accommodate 4,000 people on cruise ships to help to spread the load.

New Orleans

An estimated 50,000-100,000 people were left stranded in New Orleans for several days after Hurricane Katrina swept through.

These were people who either chose to stay or were unable to flee along with the 400,000 city residents who left as the storm advanced.

A massive airlift combined with huge bus convoys on Saturday 3 September moved thousands to safety. Many were taken to the Astrodome and other large venues in Houston. By Sunday 4 September, New Orleans was almost deserted.