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Snowflakes

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Snowflakes on a some branches
Snowflakes are a fascinating weather element, which are often associated with the Christmas period. Find out more about how they are created.

Key Points
  • Snow crystals form in the shape of a hexagon with an infinite number of variations.
  • Snow flakes are generally irregular in shape and only 1% of them are thought to be symmetrical.
  • If there is no wind the flakes can be large as they can be made of a large number of snow crystals
Christmas Features

White Christmas Origins
The Perfect Snowman
Events 2006 - 2007
Winter Predictions

BBC Weather Christmas

Christmas 2006


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Snowflakes have fascinated people over the ages, and not just children - from scientific thinkers such as René Descartes to the American photographer Wilson A. Bentley, also known as 'The Snowflake Man'.

How are they formed?
When water in the atmosphere is cooled below it's freezing point, it enters a 'super cooled' state. The snowflake forms around tiny dust particles in the atmosphere, which act as nuclei for condensation. The snow crystals form in the shape of a hexagon with an infinite number of variations.

What influences the shape of the snow crystal?
Mainly the temperature of the air, although the humidity also has some influence. As the snow crystal forms it can collide with other crystals, melt slightly or collide with water droplets that freeze onto them. Snow flakes are generally irregular in shape and only 1% of them are thought to be symmetrical.

As early as September there was talk in the media about a bleak and bitter winter and the promise of Christmas snow, which just goes to show how much interest there is in a 'bit of the white stuff'.

What influences the type of snow that falls?
Again, temperature is the main influence. When it is cold, the snow crystals do not stick together very easily, and so the snow that falls is dry and powdery - popular with snowboarders. The snow flakes are small and their structure is simple.

When temperatures are nearer to freezing, the snow that falls is wetter. If there is no wind the flakes can be large (up to 7cm across) as they can be made of a large number of snow crystals.





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