Did you know the largest snowflakes on record were 15 inches (38 cm) in diameter and 8 inches thick? Or that an average snowflake is made up of 180 billion molecules of water?
When temperatures within a cloud are at freezing or below and there is sufficient moisture in the air, ice crystals can form around a central particle, like dust. Once water vapor condenses and freezes, the complex pattern of a snowflake is born. A snowflake's hexagonal shape begins at the atomic level. It is here that water molecules bond together into stable crystal structures.
Check out these and other snow facts, and learn more about the science of snow.