I've always wanted to visit the Badlands in South Dakota. I've gathered, from various photographs, there are periods of the year where there is a heavy amount of green grass (example). I think the juxtaposition between the green grass and the geological formations is interesting and I'd like to visit at this time of the year. Does anyone know when the best time to do this is? I know little about the climate there and I'm entirely assuming this period of time is relatively short. Thanks.