Environment

Everything you ever wanted to know about snow (and more)

When does it stick, how is it made and when is it most likely to fall?

Countryside roads in rural Ireland covered in snow which is a rare enough occasion. Photograph:iStock
Countryside roads in rural Ireland covered in snow which is a rare enough occasion. Photograph:iStock
Dan Griffin
Thu Jan 12 2017 - 18:48

Snow is most likely to fall in the months of January and February in Ireland. During the winter months sea temperature are higher than land temperatures which means rain is more likely in coastal area but precipitation may fall as snow further inland.

According to Met Éireann, where most of the information in this article comes from, the average number of days with snow ranges from five in the southwest to 24 in the north midlands and a fall of at least 2cm is likely in most places about every two years.

The greatest depth of snow recorded in Ireland was during the winter of 1962/1963 when 45 centemeters fell at Casement Aerodrome.

Ireland tends to get less snow than our nearest neighbour because of the warming effect of the Gulf Stream and North Atlantic Drift.

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The ideal conditions for snow are close to and just below 0 degrees. These temperatures allow the snow to freeze, melt and freeze again. In the process snow crystals stick to each other, creating larger flakes.

Very slight temperature changes can make the difference between snow and rain making it difficult to forecast snow in Ireland.

Whether snow sticks to the ground depends on wind, temperature and humidity. Snowflakes that form around 0 degrees tend to be wetter and stickier.

But what is snow? Snow is formed when temperatures are low and there is moisture, in the form of ice crystals, in the air. When enough ice crystals stick together they become heavy and fall as snow.

According to the UK Met Office, snowflakes “are collections of ice crystals that can occur in an infinite variety of shapes and forms - including prisms, hexagonal plates or stars. Every snowflake is unique, but because they join together in a hexagonal structure they always have six sides.

“At very low temperatures snowflakes are small and their structure is simple. At higher temperatures the individual flakes may be composed of a very large number of ice crystals - making a complex star shape - and can have a diameter of several inches.”

Dan Griffin

Dan Griffin

Dan Griffin is an Irish Times journalist