Snow Stack Lighting

The subject of yesterday's blip, a snow-topped post, now steaming under a low winter sun this morning following fresh snowfall overnight. To my lay eye, the vapour looks to be the product of sublimation - the change of a solid directly into a gas without the intermediate steps of melting and evaporation. Or, perhaps it is simply evaporation of snow that has already melted. What, one wonders, would a pre-scientific and more superstitious society have offered by way of explanation?