5 a.m.: After weakening briefly to a tropical storm, Katrina regains hurricane status and moves on to the Gulf of Mexico.
11:30 a.m.: The hurricane is upgraded to Category 2, with the storm's feeder bands continuing to pound the lower Florida Keys.
4 p.m.: The National Hurricane Center warns that Katrina is expected to reach dangerous Category 4 intensity before making landfall in Mississippi or Louisiana. Hours later, in anticipation of a possible landfall, Mississippi Gov. Haley Barbour and Louisiana Gov. Kathleen Blanco declare states of emergency.