Anyways since Oasis Springs don't get snow, in Winter guess what I decided to do.

I actually really enjoyed the fact that it doesn't snow in Oasis Springs. I most likely wouldn't have purchased Seasons otherwise.
I would definitely like to see some picture of your Oasis Springs. I never thought about creating an abandoned town in this game. I think the backdrops would ruin the immersion for me, as they would look completely normal.

I'm not so sure if an asteroid impact would cause these high amounts of radiation to cause weather changes, but I could be totally wrong though.