The approach to Roughlock Falls in Spearfish Canyon, South Dakota. The falls are a highlight of the Northern Black Hills. I was there in late spring, when the daily thunderstorms powered the churning falls.
Mammatus Clouds & Lightning (by Kevin Aker)taken in Rapid City, South Dakota. Mammatus clouds are common during and even after a tornado. They are created by the intense mixture of updrafts and downdrafts within the storm cell.