Winter 2025/26 - General Discussion

Big snowfall events have always been uncommon or rare in Ireland, their rarity hasn't changed all that much. 2010 and 2018 were some of the most exceptional snowfall/cold spells in the history of the state, despite the very brief nature of 2018. Need not I remind that in the long-term Central England Temperature series that there hasn't been as severe cold weather at the time of year it occurred in 2018 since 1785. Ireland had its first March ice days in the digitised record (since 1942). 2010 literally smashed all-time NATIONAL records for November and December in low max and low min. This is despite the North Atlantic being in a very warm state in 2010 - the westerly flow was notably absent during a lot of that year is the reason why.

What has changed is the frequency of light snowfalls. Yes periods like the early 1970s or the 1990s-2000s were down on snowfalls compared to prior but there were still lots more light-ish falls, dustings, flakes within sleet etc. This is evidenced by the decline in days of snow or sleet falling per year. Shannon Airport had an average of 11 days of snow/sleet per year from 1961-1990. Now this period did encompass the notably cold, snowy 1960s decade which seen a fairly dramatic cooling from previous decades up to that point though was comparable to the early 20th century and not as cold as the late 19th century. This average for Shannon is now just under 6 days per year on average for the period 1991-2020 so basically halved in frequency in that time. That's a huge difference for a 30-year average - basic maths will tell you that the more variables (years) included, the more difficult it is to shift or skew the average in one direction so to see this is massive. If we take out 2010, we would probably see even more of a decrease as 2010 was an extreme outlier that likely skewed averages to some extent. We seen this skewing with the Central England Temperature where December was the only month that seen a cooling from 1971-2000 to 1981-2010 but this has since been reversed with the more modern 1991-2020.

Another station example is Belmullet seen an average of 18 days of sleet/snow falling per year from 1961-1990 which has reduced to 12 days from 1991-2020, a decrease of a third.

On a more long-term scale, there was a paper last year "A Monthly Snow and Sleet Series for the Greater Dublin Area 1867–2024" which showed further evidence of the decrease. Look how "snowy" the late 19th century was with many big seasons - most notably the winter of 1878-79. Note the season goes from October to May and the year is of January. The last extreme snow season (2 standard deviations above normal) in the Dublin area was 1978-79. The biggest seasons since were 2009-10, 2010-11 and 2017-18. This does not take account for how much snow fell or depths which is a very different matter. 2023-24 was the first winter in the series to have had snow/sleet falling for one single day (I'm sure we remember it well, March 1st). Interestingly, the running average is not yet at the low point that it was through the 1940s when the North Atlantic was also in a notably warm state showing there is some degree of correlation likely with the Atlantic sea surface temperatures and the frequency of snowfall in Ireland. Unless we see a dramatic flip like the 1960s, it is likely that the running average will equal or even be worse than the previous low point.

However, one point I will argue that if blocking does align to allow a clean easterly flow or we get a big low against a cold flow, I think there is the potential for even bigger snow events with all the added moisture in the atmosphere to draw from the warmer sea temperatures. The trouble (or again relief for many) is getting that clean flow in the first place to allow a sufficiently cold airmass filtered this way.

This paper can be read here for those interested ~ https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/gdj3.70022.

Individual station averages can be read here though it is limited ~ https://www.met.ie/climate/30-year-averages Snowfall in Ireland