Hurricane Katrina started Aug. 23, 2005, and made landfall in the Gulf Coast on Aug. 29, 2005. Once it made landfall, it continued to rage until later that same day when it was downgraded to a tropical storm.
What most people think of as Hurricane Katrina lasted for half the day of Aug. 29, 2005. However, the actual hurricane was active in the ocean for several days before then, and the tropical storm it became for several days after. Nearly 2,000 people were killed during this time, 900 people declared missing and some 90,000 square miles of the United States were adversely affected.