The chemical formula for snow is H2O. It is the same chemical formula as water, as snow is made up of one or a series of crystals of ice.
A snowflake is either an individual snow crystal or a series of snow crystals stuck together; therefore, its chemical formula is the same as water. Snowflakes have symmetrical patterning, unlike sleet particles which do not have this type of patterning. The ice crystals that make up snow are a six-fold symmetrical pattern. They resemble hexagonal prisms. As snowflakes grow, they tend to branch out and make more complex shapes than simple hexagonal prisms.