Hurricane Katrina hit New Orleans on Aug. 29, 2005. When it hit the city, it was a category 3 storm, with winds moving between 100 and 140 miles per hour.
Though the winds themselves did significant damage to the city, the storm surge of water accompanying the storm did more. When the surge of water hit the levees that protect New Orleans from flooding, many of the barriers broke under the strain, causing massive amounts of water to inundate the city. In total, Hurricane Katrina did an estimated 108 billion dollars in damage, making it the costliest hurricane in American history. The hurricane's remnants finally dissipated over Canada a few days after it first hit land.