The weather seemed to go crazy across the Great Plains and Midwest over a two-week period from May 17 through May 30. Those 14 days produced 262 tornadoes.
Fifty of those tornadoes produced at least EF-2-scale damage (wind estimated at more than 110 mph), including 18 EF-3 (wind estimated at more than 135 mph) and two EF-4 (wind estimated at more than 165 mph); one in Linwood, Kansas, and one in Dayton, Ohio. The tornadoes have been directly responsible for the deaths of seven people, bringing the total number of U.S. tornado fatalities this year to 38.
This is not an inordinate tally of tornadoes or of tornado fatalities for a year or even for half a year. However, this is a very high concentration of tornadoes for a two-week period.
A pattern of a strong southwesterly upper-level wind with numerous embedded swirling impulses flowing over south to southeast surface wind combined with sufficient heat and humidity is responsible for the severe weather outbreak.