April 3, 1974. Across America, many people wake up this morning thinking it will be a normal day. But in the next 24 hours, almost 150 tornadoes will hit the United States. It will be the largest tornado outbreak in the nation's history. Why did so many deadly tornadoes hit on this one day? And how did it spur life-saving changes that are still with us decades later?

Thank you to our guests: Greg Forbes, former severe weather expert with the Weather Channel; and atmospheric sciences professor Jeff Trapp from the University of Illinois.

**This episode originally aired March 29, 2021.

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