Here's the sitch:
It's about three generations after a huge war involving nuclear bombs and biochemical warfare. Long enough ago that not a lot of people are still alive that saw it first hand, but recent enough that the effects of the radiation and biochemical agents are still pretty prevalent.
Is there a possibility that there could still be radioactive rain clouds (like what happened over the Pacific and Europe after Hiroshima/Nagasaki and the Nevada nuclear tests, respectively)? Is there a possibility that any biochemical agents could have gotten into rain clouds, causing contaminated rain? If so, which agents should I look at?
Search ideas are more than welcome too ^_^