Freezing conditions are on their way. But what is causing this cold snap?

The trouble has its origin in the polar vortex. That is the large mass of cold air in the upper atmosphere or stratosphere over the North Pole that separates it from the warm air further south.

Normally the vortex causes air to move from west to east.

But around two weeks ago, it suddenly warmed, jumping in temperature by up to 50 degrees celsius.

This disrupted the vortex, causing it to break up and pushing a mass of cold air in a southwesterly direction instead.

Gradually that has made its way down over Europe, causing significant snow fall in many places across Europe and the UK. And it is this cold air mass that will arrive on our shores today.

But there is an added complication.

As that polar mass moves over Ireland, a storm system named Emma by Portuguese forecasters is moving up from the south.

It is carrying warmer moist air and high winds.

And when, as expected the two masses meet, that moisture will be turned to snow with wind generating blizzard like conditions.

Already, comparisons are being made to the "Big Snow of 1982".

We will have to wait and see if indeed it is that bad. But in the meantime, experts are warning that people should not take anything for granted.