24 DECEMBER 2020 Found mostly in the open prairies of North America and some remote regions of Northern Europe, snow doughnuts or snow rollers might look like icy man-made structures, but these tire-shaped curiosities are entirely natural.
They're very rarely seen because the number of weather conditions that need to be just right for them to form – including wind, temperature, snow, ice, and moisture – is pretty astonishing. So how do they form? It turns out you need: A relatively thin surface layer of wet snow on the ground Under that layer, there needs to be a substrate the wet snow won't stick to – for example, ice or powder snow