I’ve been working with the weather effects and while in editing mode the snow preview is not showing up but when I am previewing the effect in-game the snow and rain are rendered. Seems to only happen in the StarterGame as the BeachCity preview the effects work correctly.
Sorry for the inconvenience.
You might want to turn on AI/Physics to preview weather effect in viewpoint
There is also a known bug that enable / disable AI/Physics crashes editor. Team is looking for the solution to fix the issues.
Give it a try and us know if you have any question.