I suppose, technically, if the conditions were right, South Dakota could have a tornado during any month of the year. However, our state is usually under the tornado gun from April through September. Thunderstorms that bring tornadoes are most likely to develop in the spring and early summer. But, of course, there are outliers. Digging through the data from the NOAA Storm Events Database, we can find every tornado that's touched down in South Dakota since 1950.