Snowflakes or snow crystals form when ice crystals freeze around tiny particles of dust that are in the air and join together as they fall. Ice crystals that melt as they fall become rain. Ice crystals that form near the ground are called frost.
Winter snow, ice, and wind can be rough on rose vines and shrubs. With some simple precautions, you can keep your roses protected through the cold months and ready to bloom again when the warm weather returns. - Garden Tips and Trick