1975 Omaha tornado outbreak

During the afternoon of May 6, 1975, at least 12 tornadoes touched down in the Upper Midwest. The costliest of these tornadoes struck parts of western Omaha, Nebraska, causing at least $150 million in damage and killing three people. It was at the time the costliest tornado in U.S. history, damaging over a thousand homes across a nearly 2,000-block area on its roughly 15 mi (24 km) long path. The tornado's damage was later rated F4 on the Fujita scale. Another F4 tornado struck Magnet, Nebraska, destroying or damaging nearly every building in the town. The tornadoes were produced by thunderstorms moving across a narrow region of warm and moist air that had advanced northwards into the Upper Midwest as a result of a strong area of low pressure over South Dakota. Additional tornadoes on May 7 and May 8, including several in Louisiana, Texas, and Mississippi, were associated with the same storm system.