A snowflake begins to grow as an ice crystal around a small speck of dust in a cloud. As the crystal grows it falls through the air in the cloud and joins with other crystals to make snowflakes. The crystals in a snowflake make the shape of a star. This star shape has six arms. It offers lots of resistance to the air as it falls and so parachutes to the ground rather than dropping like rain.

If the temperature of the air is about 0°C the snowflakes make wet snow on the ground which is good for making snowballs. If the temperature of the air is below 0 °C the snowflakes make a dry powdery snow which is no good for making snowballs.