Like rain, snow is formed by condensation of cloud drops. When the temperature in the cloud is above 0 ℃, there is no ice crystal in the cloud, only small water drops, and it will only rain. If the temperature of the air in and below the cloud is lower than 0 ℃, small water droplets will condense into ice crystals and snowflakes and fall to the ground.
Snowflakes are beautiful crystals, which form snowflakes when they are falling in groups. The size of a single snowflake is usually between 0.05 and 4.6 mm. The snowflakes are very light, and the weight of each snowflake is only 0.2-0.5g. No matter how light and wonderful the snowflakes are, their crystals are regular hexagonal shapes, so the ancients said that "there are more than five flowers of vegetation, and six snowflakes alone".
The shape of snowflakes is closely related to the moisture conditions during their formation. If the water vapor in the cloud is not too rich, only the surface of the ice crystal reaches supersaturation. If the water vapor is a little bit more, the edge of the ice crystal also reaches supersaturation. If the water vapor in the cloud is very rich, the surface, edge, and corner of the ice crystal reach supersaturation. Its sharp corners are prominent, getting the most water vapor, and the coagulation growth is the fastest, Therefore, most of them form star shaped or dendritic snow crystals.