The National Hurricane Center says Katrina continues to grow stronger, with maximum sustained winds at 175 miles per hour.
A hurricane warning went into effect Sunday for the Gulf Coast from Morgan City, Louisiana, to the Alabama-Florida line. A warning means hurricane conditions are expected within 24 hours.
The Hurricane Center says the Category Five storm has the potential for storm surge flooding of up to 25 feet, topped with even higher waves. Forecaster also say as much as 15 inches of rain is possible.
In New Orleans, the mayor has ordered a mandatory evacuation ahead of the powerful storm, saying anyone who can leave the city should.
New Orleans is considered especially vulnerable because it sits below sea level, and needs levees and pumps to keep out water.
Meanwhile, President Bush has declared states of emergency in Louisiana and Mississippi to accelerate the emergency response to Hurricane Katrina.