Earliest day on which Memorial Day can fall, while May 31 is the latest; celebrated on the last Monday in May. (United States)
Earliest day on which Mother's Day can fall, while May 31 is the latest; celebrated on the last Sunday in May. (Algeria, Dominican Republic, France (First Sunday of June, if Pentecost occurs on this day), Haiti, Mauritius, Morocco, Sweden, Tunisia)
1955 - In the United States, a night-time F5tornado strikes the small city of Udall, Kansas, killing 80 and injuring 273. It is the deadliest tornado to ever occur in the state and the 23rd deadliest in the U.S.