Hmm, odd, I found that button but it is greyed out.

Thanks for the suggestion though. If I want to see snowflakes I’ll can switch to another workspace or look out the window and wait a few days. :)

Edit: When I turn on a compositor, picom, the option becomes clickable. But when I turn on picom, the flakes stop rendering for some reason. It looks like somebody came up with a patched version for i3 + picom, so I guess this is a problem that people have worked on already.