This is an interesting topic, especially as we ourselves near a time when we'll be able to control the weather. Weather manipulation in stable environments could also be a source of conflict between groups. Where I live, Pacific Northwest, we get atmospheric blasts of South Pacific moisture throughout the year. Let's say our neighbours to the south decided to redirect this weather stream for their own purposes. Suddenly, we would find ourselves in dire straits water-wise, and we would not be a happy bunch. In your world, the weather is more extreme, but I can see a similar situation developing. Great world building topic.