1974 Super Outbreak

The 1974 Super Outbreak was one of the most intense tornado outbreaks on record, occurring on April 3–4, 1974, across much of the United States. It was one of the deadliest tornado outbreaks in U.S. history. It was also the most violent tornado outbreak ever recorded, with 30 violent (F4 or F5 rated) tornadoes confirmed. From April 3–4, there were 149 tornadoes confirmed in 13 U.S. states and the Canadian province of Ontario. In the United States, the tornadoes struck Illinois, Indiana, Michigan, Ohio, Kentucky, Tennessee, Alabama, Mississippi, Georgia, North Carolina, Virginia, West Virginia, and New York. The outbreak caused roughly $600 million USD (equivalent to $3.92 billion in 2025) in damage. The outbreak extensively damaged approximately 900 mi2 (2,331 km2) along a total combined path length of 2,600 mi (4,184 km). At one point, as many as 15 separate tornadoes were occurring simultaneously. The 1974 Super Outbreak was the first tornado outbreak in recorded history to produce more than 100 tornadoes in under a 24-hour period, a feat that was not repeated globally until the 1981 United Kingdom tornado outbreak and in the United States until the 2011 Super Outbreak, the largest outbreak on record by number of tornadoes in a 24-hour period. In 2023, tornado expert Thomas P. Grazulis created the outbreak intensity score (OIS) as a way to rank various tornado outbreaks. The 1974 Super Outbreak received an OIS of 578, making it the most intense tornado outbreak in recorded history.