Since the formal start of naming during the 1947 Atlantic hurricane season, an average of one Atlantic storm name has been retired each year, though many seasons (most recently 2014) did not have any names retired. The deadliest storm to have its name retired was Hurricane Mitch, which caused over 10,000 fatalities when it struck Central America during October 1998. The costliest storms were hurricanes Katrina in August 2005 and Harvey in August 2017; each storm struck the U.S. Gulf Coast, causing $125 billion in damage, much of it from flooding. The most recently retired storm names are Laura, Eta and Iota.