The 2017 version of the /r/Overwatch snow effect. We use a perspective-enabled container to give the snow depth. This also 3d accelerates the effect, greatly reducing CPU usage. You can adjust the snow in various ways, but this is probably the simplest with a low performance hit but still a good effect.
For 2017, we added some layers to the snow scene with characters having a snowball fight. We simulate depth of field by blurring the furthest snow effect manually, and increasing the density a bit to help the browser scale far objects. We use a mix of translateZ and simply scaling down the snow to add depth.
We're not really matching how slow or fast the snow might be at the distances we're showing it, but thats OK for the purpose of this demo.
/r/Overwatch usualkly has a blurred menu bar that we would previously add a blurry snow layer to match that for. We ditched that this time for simplicity, since our CSS was over 100kib long and eliminating the blurred menu bar code allowed the snow to fit in the stylesheet nicely.