Making snow&rain "affect" some things?

[FlawlessHappiness]

That would either look choppy or would be performance heavy.
You need to remember that such a refresh rate should be the same as player's FPS.
Creating and Removing a ParticleSystem 30 times a second or more might be too much.

But I didn't try it, so... you still might want to give it a go.

I was thinking 10 times a second. It's not like the player has lightning speed anyway