IT is said that Charles Dickens is single-handedly responsible for our dreams of white Christmases with treetops glistening in the snow. Dickens was born in 1812 during the coldest decade of the 19th century when the winters were so cold it was known to freeze over the river Thames, it is even referred to as a ‘Mini ice age’ in some scientific texts.

It is likely that his nostalgic memories of these cold winters were his inspiration for the snowfall on Christmas Day in his renowned novel ‘A Christmas Carol’ first published in 1843, and therefore our association that on the 25th of December there will be snow.

For Christmas day to be officially considered white, only one snowflake has to be observed to fall anywhere in the UK. A single snowflake has indeed fallen 38 times in the past 54 years, but it’s not really the complete white out that we would hope for. A widespread fall of snow that would remotely resemble the wintery scenes in our Christmas cards and movies has only happened four times in the past 51 years.

If you are lucky enough to catch one of these elusive snowflakes then have a good close look. You may notice that it is symmetrical and that it is a hexagon, with six sides. You might think that a snowflake is simply frozen water, but it’s a little bit more complicated than that. Our hexagon snowflake looks a bit different from an ice cube, wouldn’t you agree? That’s because while an ice cube is frozen water, our snowflake is frozen water vapour.

Water exists on our planet in what we call the three main states of matter: solid, liquid or gas. The solid form of water is called ice, the liquid form of water...is simply water, and the gas form is called water vapour.

We can see these states in the freezing and cooling of water. If we were to heat a pan of water it would start to bubble and boil into water vapour. This water vapour will eventually cool down and turn back into liquid water, which we can see on our windows on a cold day as condensation, or even in our breath as we breathe out when we are outside in the winter. When we put liquid water in the freezer it will cool down and freeze into a solid.

Our snowflake crystal starts life as a tiny speck of dust or pollen that catches water vapour out of the air. When it is very cold, the water vapor will freeze and form an ice crystal. This is the beginning of our snowflake. But why is it a hexagon shape?

Water molecules, when in a liquid or in a gas state, zip around and bounce into each other. When water gets cold enough these molecules slow down and, as the water freezes, they start to arrange themself in the most efficient way.

Each snowflake has a unique pattern because each one follows its own path to the ground; it gets blown about in the wind and bumps into different water molecules in the air. Changes in temperature and humidity will also cause a change in their design. The designs can change from flat hexagons called plates or long thin hexagons called needles or columns.

A recent study by the Cairngorms National Park and ClimateXChange showed that there may be a significant reduction of snowfall in Scotland in the future due to climate change, so in future years the chance of a white Christmas could be slim.

Tune in to GSCAtHome’s festive science programme everyday from 21 December to 1 January at 10am to find out the little changes you can make to help combat climate change and make Christmas snowy.