The massive storm that became known as Hurricane Katrina originated from a tropical depression that began in the Bahamas on Aug. 23, 2005. The remnants of Katrina caused storms through the central United States before it deteriorated into a frontal boundary in southeastern Canada on Aug. 31, 2005.
After striking the Gulf Coast at New Orleans, the hurricane continued into Mississippi. It caused major flooding and evacuations between August 28 and August 29. The storm was reclassified to a tropical depression after it broke in half in Tennessee. Even after the downgrade, the heavy wind and rains in the central U.S. and in southern Canada wreaked havoc, explains History.com.