Yes there are 4 seasons in this part of the country, but there are not that many trees outside the main city, but there are state parks nearby to drive too. In my opinion the fall colors in South Dakota aren't as good as some areas due to the tree species south dakota has.
You'll get better fall colors in eastern MN and all of Wisconsin where you find more natural stands of birchs and maples which has better fall colors than the South Dakota native species. I find the best colors in South Dakota to be in towns where non native species are planted. Southern WI, northern MN, Michigan, and eastward have the best fall colors. Maine, etc.
In summary.. yes there's 4 seasons in Sioux Falls and ample precip to keep it green in the summer.
Sioux Falls has great fall color too, but the countryside, I find mostly the same dull brown color with the native tree species. You can tell when someone's planted a non native.