A localized, but devastating series of severe thunderstorms affected the Great Lakes region during May 20-21, 1953. The strongest of these storms produced three intense, long-tacked tornadoes in Iowa, Michigan, and Ontario. The worst tornado event was a violent F4 tornado that tore through the cities of Port Huron, Michigan and Sarnia, Ontario on May 21, damaging or destroying hundreds of structures and causing dozens of casualties. Overall, the tornadoes killed eight people, injured 123 others, and caused at least $17.6 million (1953 USD) in damage. Thunderstorm winds also caused an additional fatality when a tree fell on a house in Waterloo, Iowa.