Configure weather effects

I was putting this together as two separate suggestions, but I realized they're basically the same thing.

First, the ability to select an area to be affected by weather effects (currently there's only snow, but later they could add things like snowstorms, blizzards, rain, etc.). For example, if you create a map where you enter a cave and activate the "snow" weather effect, the entire cave is covered in snow, when it should only be up to a little beyond the entrance. It would be great to be able to configure which parts of the map have snow and which don't (the same would apply to rain; it shouldn't rain inside the entire cave).

Second, a less intense snow effect. Currently, the snow is so thick that you can't see many things (like trails).