The tee box on hole 6 in Springfield is on my top 10 list for prettiest views in the state
Beautiful area, and still close enough to Yankton if you really needed a decent-paying job. Hot Springs is in a beautiful area of the state, check out Custer as well. Parkston might be worth checking into. It's a decent town and close enough to Mitchell for shopping and job opportunities. Platte is a decent town close to the Missouri River. With all the small towns, schools can be hit or miss. Either way, small class sizes can be a benefit.
Weather-wise it sounds like the heat won't be an issue for you. The humidity may get you though if you end up east of the Missouri River. It's a different kind of humidity here than closer to the coasts - the moisture gets sucked out of the ground and plants rather than from the ocean. It feels generally "heavier" to me. The cold may be a shock. East river more than in the west, and especially if you end up in the northeast part of the state where Webster is. The growing season is a few weeks shorter up there as it gets colder earlier and warms up later in the spring. Add in the wind, and it can be unpleasant even for those that have lived in it all their lives.