The Lubbock tornado, a F5 tornado, hits Lubbock, Texas, killing 26 and causing $250 million in damage.
Portions of Lubbock, Texas, were struck by a powerful multiple-vortex tornado after nightfall on May 11, 1970, resulting in 26 fatalities and at least $135 million in damage. It was in its time the costliest tornado in U.S. history, damaging nearly 9,000 homes and inflicting widespread damage to businesses, high-rise buildings, and public infrastructure. The tornado's damage was surveyed by meteorologist Ted Fujita in what researcher Thomas P. Grazulis described as "the most detailed mapping ever done, up to that time, of the path of a single tornado." The most severe damage was assigned an F5 rating by Fujita when he introduced his eponymous scale for rating tornadoes in 1971. The extremity of the damage and the force required to displace heavy objects as much as was observed indicated that winds produced by vortices within the tornado may have reached as high as 290 mph (470 km/h).
Although skies were clear, dry, and sunny in Lubbock during the afternoon of May 11, the westward push of a dry line brought moist air into West Texas, providing suitable conditions for thunderstorm development. After 6:30 p.m., thunderstorms were in progress over the Lubbock area. At least two tornadoes developed prior to the main F5 tornado, including one that tracked across parts of eastern Lubbock near U.S. 87. The primary F5 tornado touched down in southwestern Lubbock at 9:35 p.m. and over the next half-hour carved a 8.5-mile (13.7 km) path of devastation encompassing roughly a quarter of the city, with the twister lifting near the Lubbock Municipal Airport shortly after 10 p.m. The tornado varied in size, spanning 1.5 mi (2.4 km) across when it first touched down before narrowing to around 0.25 mi (0.40 km) by the time it lifted. Severe damage was wrought to high-rises and other buildings in downtown Lubbock, including the 20-story Great Plains Life Building. The tornado briefly moved west and weakened, causing light damage to the campus of Texas Tech University before reintensifying and resuming a northward path. The tornado's most destructive impacts were observed in the Guadalupe barrio, north of 4th Street, along Texas State Highway 289, and near the Lubbock County Club. In those locales, some homes were completely leveled and many others were irreparably damaged. Around 119 aircraft were damaged at the Lubbock airport where the Lubbock office of the United States Weather Bureau was located.