Ok, no it’s not rain but here’s what I’m thinking, I was on a map, and not you can’t edit it sad face, any way, it had rain, now I was wondering if, you can make it so that their are leaves falling, but not all over the map in like a particular area (were their is trees) oh and is waves possible in source, it’s not something I’d like to make just want to know :).

You’d need to find a chum to do particles for you. Or you could learn to do them yourself.

you can change the material used for func_precipitation type ash into leaves and pakrat it
thats a cheap easy trick way to do it