The size and shape of a snowflake are determined by the air temperature in the cloud and humidity. No two snowflakes are exactly the same. Each snowflake takes a slightly different path from the sky to the ground and encounters slightly different atmospheric conditions as it falls. This gives each snowflake a different growth rate and shape. When you look closely at snowflakes many times they look broken or they look like a clump of snow crystals. This is from colliding or sticking to other snowflakes as they fall to the ground.
