When does the water turns in to a snow??

Water turns into snow at temperatures above -40 degree Celsius. Snow forms when water in clouds freezes into tiny ice crystals. This moist air freezes around minute dust particles or chemical substances floating in the clouds. These particles become the core or the nucleus of each crystal. Such crystals grew in size when more water crystallizes around a particular nucleus. This happens if the air is more humid. Snow flakes are formed when a number of crystals join together in clusters. The structures of snow flakes are often beautiful, hexagonal form. It is believed that no two snowflakes can be identical. These fall from the clouds on to land as snow.