Weather - Snow and rain effecting objects

Hello everyone,
I was wandering…
is it possible to make so that objects will a layer of snow on top of them when I have snow falling?
And something similar with rain. To have rain drops effect on objects while i have rain falling.
I was thinking about something like in cryengine where you can trigger a layer of rain or snow to effect the model.

Snowscape: Snowscape for Unity 3D - YouTube


SnowPrefab: Unity3d Prefab - Snow! (particle FX) - YouTube

Someone has done it for snow: Snowscape | 3D Environments | Unity Asset Store