28 tornadoes touched down in Iowa, Illinois, Ohio, Georgia, North Carolina, Maryland, Virginia, and Tennessee.

An upper level disturbance across the northern Great Plains interacted with a warm and moist air mass on the afternoon of June 12.

[1] Between 3 and 4 p.m. CDT (2000–2100 UTC) on June 12, numerous supercell thunderstorms developed across Iowa, Illinois, Wisconsin, and Minnesota.

[5] The supercell activity in Iowa and Illinois congealed into a powerful squall line as the storms moved into Indiana later that night.

The newly formed derecho began producing numerous reports of damaging winds in northern Indiana.

[6] The derecho continued into Ohio and produced widespread damaging winds across much of the state, along with several embedded tornadoes.

[12][13] The derecho downed numerous trees and damaged structures in West Virginia as well, with surveys indicating winds up to 80 mph (130 km/h) in some areas[14] In Maryland, the derecho produced an unusually fast moving, long track EF0 tornado that tracked through several northern DC suburbs, downing many trees, several of which landed on homes.