Normal and high-speed footage of a cloud-to-ground lightning strike triggering upward lightning from three television towers. The action is shown at normal speed first, and then at 1.7% of normal speed (slowed down nearly 60 times). The first cloud-to-ground strike (right) trigger streamers and upward discharges from the three tall towers at left, as the local electric field was greatly enhanced. Filmed in Rapid City, South Dakota, USA, in summer.