This post will get you started. Snow and Rain are the same mechanism in the Worldbuilder. Just change the texture and buoyancy so the snow floats around.
https://www.coh2.org/topic/66696/rain/page/1#post_id646642
Here is an example that can get you started:
Speed - How fast the snow moves/falls.
Randomize - Adjust the movement/direction.
Density - How much snow is falling. Too much kills players FPS. Less is more.
Particle Buoyancy - How much it floats.
Width/Length - The size of the snow. Actually the snow texture size.
Tile U/V: How much of the texture to use 0 = None, 1 = All, 2 = Two repeats, 4 = 4 repeats, etc.
UV COORDINATE EXAMPLE:
Thank you very much for this