Warning: contains some graphic imagery

August 23, 2006—One year ago today, the National Hurricane Center in Miami, Florida, issued its first warning about a tropical storm forming over the Bahamas. By the next day, that storm had grown strong enough to be given a name: Hurricane Katrina.

The powerful hurricane battered U.S. Gulf Coast cities and spurred subsequent flooding in New Orleans, Louisiana. Over the course of about a week, the storm and its aftermath caused record damage that may rank Katrina as the costliest natural disaster in U.S. history.

Follow a day-by-day account of the storm's wrath, from its birth in the Atlantic Ocean to its catastrophic effects: flooded streets, flattened homes, and horrific loss of life.