It would be nice if weather varied over time, like rain and storm not being constant.

Thanks for the idea. The weather here is static by design: it's built from planet-level particle effects that the game runs all the time, and the fog and colour grading can't change while the game is running at all. Making rain and storms come and go would mean rewriting the effects as a runtime script, so I don't plan to do that.

I know that RealRain managed to do it, you could give a look at its code, it might help you.

Thanks, I know how Real Rain does it. This mod is static by design, and making a dynamic weather mod like that isn't in my plans.