Thinking Outside the Classroom: Why are no two snowflakes alike? |

Thinking Outside the Classroom: Why are no two snowflakes alike?

Brent Beadles
Thinking Outside the Classroom

If you are like us here at the Keystone Science School, you are giddy every time you see that precious white frozen precipitation falling from the sky. We are talking about snow, of course. We love building snow people, snow forts and riding deep powder. Have you ever thought about how snowflakes form, why there are so many types of snowflakes, or why each snowflake is unique? At Keystone Science School, we strive to inspire curiosity through the lens of science. If you are curious, keep reading.

Snow starts out as moisture in the atmosphere. Clouds form when moisture in the atmosphere condenses onto small particles to make water droplets. If there is enough moisture in the air and the air is cold enough, some of the water will start to freeze. Ice requires a special particle in order to freeze and grow that is less commonly found than the particles that make water droplets. If the perfect recipe of temperature, moisture and freezing particles exists, then ice starts forming.

At this point in a snowflake’s life, it is just a tiny crystal of ice that is smaller than a fine grain of sand. So how does it grow into so many unique forms? Snowflakes grow in two ways. Moisture will either freeze to the pre-formed ice crystal or the ice crystal will collid with water droplets. The first type of growth depends on temperature and available moisture in the cloud and atmosphere. In certain temperature and moisture conditions, the snow will grow into columns or needles. In other conditions, the snow will form a six-sided plate and can grow along its edges to create dendrites. Dendrites are the six-sided star-shaped crystals with intricate branches that are usually associate with snowflakes.

The second type of snowflake growth occurs when the ice crystal bumps into water droplets and those droplets freeze onto the crystal. This freezing of water droplets onto the ice crystal will round out or fill in the shape of the crystal, which make it more spherical.  

At this point, the snowflake will continue to grow bigger and bigger. Once a snowflake becomes big enough, it will outweigh the updraft forces that are keeping it afloat, and it will fall toward the ground. On its journey to the ground, the snowflake will pass through areas of different temperatures and moisture conditions.

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So why is each snowflake unique? It is because each snowflake has a slightly different path to the ground, and the conditions in the atmosphere are constantly changing. On its way through the cloud, it might bump into more water droplets or other snowflakes. Once a snowflake is out of the cloud, some areas might help the flake grow intricate branches while other areas might help it grow as a column. As each snowflake falls, it continues to grow and evolve until it finally comes to rest.

As the snow starts to accumulate this winter, go out and discover these unique crystals. Are they more like a column, a plate, a dendrite (six-sided star) or a sphere? Are there multiple crystals clumped together?

You can learn more about snowflakes and their creation with a few simple instruments. Try putting some snow on a dark background — such as a glove, jacket sleeve or small piece of fabric — and view it with a simple hand-held magnify glass. With each snowfall, you will notice that unique layers build on the snow, which continues to evolve throughout the season based on weather events.

Get outside and be a curious learner of the snow. Happy snow days!

Thinking Outside the Classroom is written by the staff at Keystone Science School. Contact the school at

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