This mod looks really wonderful so far, and I'm sure this is beyond the current scope of the mod, but it seems like you have great potential here to make a system designed for implementing custom weather/particle effects via a config or json files, and customizing existing ones. Resource packs can be used to alter or add particle textures, and their behaviors can be defined by a json file, allowing for things like specifying biome type/temperature, size, duration, gravity, etc.

Essentially you could make a system for others to easily design their own particle weather by allowing for extensive configuration. I'm by no means saying this is something you have to do or even should do, it just seems like it could be a cool direction to take the mod given its promising foundation so far!

perhaps :)