2 a.m.: Katrina escalates to Category 4 strength, heading for the Gulf Coast. The last time Mississippi or Louisiana saw landfall from a Category 4 or stronger storm was 1969 with Hurricane Camille.
7 a.m.: Hurricane Katrina intensifies to Category 5, the worst and highest category on the Saffir-Simpson scale.
10 a.m.: As Katrina hits 175 mph winds, New Orleans Mayor Ray Nagin orders mandatory evacuations as the storm seems to beat a direct path to the city.
During the day, Bush declares a state of emergency in Mississippi and orders federal assistance. The National Hurricane Center says low-lying areas along the Gulf Coast could expect storm surges of up to 25 feet as the storm, with top sustained winds of 160 mph, hits early the next day.