Snow is frozen form of rain. It usually comes during the winter season. After a snow storm it collects into piles on any surface from the streets to the trees.
Often snow is associated with Christmas, which also occurs during the winter season.
When fighting the Sinister Six, Spider-Man sprayed Sandman with water then covered him with snow so that he froze completely. However, before he could be captured by the authorities, Master Planner and the Tinkerer freed him.