It could be worse. In mid-November 1919, for example, the temperature at Markree Castle in Co Sligo fell to a chilling minus 11 degrees. And a little further back, on November 19th, 1807, when severe blizzards affected the whole country, there was great loss of life when two ships, the Prince of Wales and the Rochdale, both bound for Holyhead, went aground near Blackrock in Co Dublin; because of the very heavy snow, the crew were unaware they were so close to land.
A more meaningful statistic, however, is that on a typical November day we might expect the temperature to rise to around 10 or 11 degrees, in contrast to the few degrees above zero we are promised for the next few days.
The immediate reasons for the cold snap are easy to see from the weather map. Instead of the air flowing towards us over the relatively balmy waters of the Gulf Stream, as usually happens, it is instead sweeping down in our direction from the Arctic wastes to the north of Norway.
Having spent several days in direct contact with a sheet of ice, it is scarcely surprising that the air is cold, but its chill is exacerbated by the strengthening winds. Low temperatures in themselves are not particularly unpleasant when the wind is calm. In such circumstances we are encapsulated in an envelope of stationary air whose inner-most layers adapt to the body temperature, insulating us effectively from the cold.
But a cold wind quickly carries away whatever heat our bodies may produce and the stronger the wind the colder we will feel.
For example, with a wind of 32km/h (20mph) and a temperature of six degrees, the average individual feels much the same as he or she would feel if the temperature were minus two degrees in calm; with that same wind, a temperature of zero feels like minus 12, and if the wind is blowing at gale force, around 64km/h (40mph), zero feels like a bitter minus 17.
If this cold weather comes as a surprise, it may be because our winters for the past 10 years have been unusually mild.
It is for this reason that the recent predictions of a harsher than usual winter by the British Met Office have received so much attention. But these allegedly alarming forecasts should be seen in context.
Firstly, the Met Office is not predicting very extreme conditions; it says merely that this winter may be more like the winters we used to get during, say, the 1980s, than the very mild ones we have become accustomed to of late. And the Met Office itself is at pains to point out the tentative and experimental nature of its conclusion.