Norman said: Can you not do this using the foreground layer? I've recently used it for a moving fog and a blizzard and it seems to do what you're asking for You can do this now with Animations, like mp4, GIF, webm formats. And, the Roll20 Marketplace has a lot of those: <a href="https://marketplace.roll20.net/browse/search?category=Art:Weather" rel="nofollow">https://marketplace.roll20.net/browse/search?category=Art:Weather</a> But, the OP seems to be asking about using FX (particle effects) to do it, instead of GIF's. FX (effects): <a href="https://help.roll20.net/hc/en-us/articles/360037258714-Effects-FX-Tool" rel="nofollow">https://help.roll20.net/hc/en-us/articles/360037258714-Effects-FX-Tool</a>