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Irish Weather Statistics
Comments
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I said in the summer thread that Casement was experiencing its windiest June in 31 years. On a more national level, it hasn't been as impressively windy but still windier than average. Currently it's comparable to June 2022 which was the windiest since 2017. Both were notably westerly Junes.
Photography site - https://sryanbruenphoto.com/
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It is now 70 years since Ireland experienced its sunniest of any month on record, that being July 1955. I've mentioned this month many a time but I don't believe I ever did a proper historical post on it so this is going to be it.
It should be first mentioned that 1955 as a whole was known as a pretty blocked year with a cold winter including noteworthy snowfalls and a prolonged cold spell in February, a spring that was highly varied but at first very dry with record breaking sunshine in March followed by a very dry April and a wintry May. The blocked theme continued into much of the summer which was a warm and dry one after a poor June and then autumn similarly was rather blocked though September was westerly. December ended the year on a benign westerly, mild note.
The blocking theme of 1955 is illustrated below by NCEP Reanalysis for SLP anomaly across Europe with a strong signature for negative North Atlantic Oscillation (NAO) conditions indicated by well above average pressure over Iceland and deep low pressure over the Azores with a very southerly tracking jet stream. The year as a whole was cool but as mentioned, the summer was the exception with very warm conditions, especially in August. I consider it one of the more interesting weather years in our historic record up with 1947 and 1995.
The summer of 1955 did not start off on a good note. June 1955 was a poor month. The first week was very wet with a series of southerly tracking low pressure systems coming up against blocking to the northeast. Daily falls of 10mm+ were very common on a widespread basis and most in the south and east had reached more than their entire average June rainfall after the first week. Dublin Airport had 83.0mm of rain in the first 7 days of June, one of its wettest 7 day periods on record. Other stations had nearly 90mm in the same period including Balbriggan and Rathfarnham Castle. The highest total at lower ground I was able to find was at Garristown in North County Dublin which had 108.9mm fall in the first 7 days. Glencullen a bit higher up had 136.2mm in the same period and 156.2mm in the first 8 days. East Leinster was about the worst spot to be for this as the battle zone between the anticyclone and the low pressures was pretty much placed perfectly here. I can imagine a lot of run off in the Wicklow Mountains led to flooding but I don't have evidence of this. 100mm+ totals were common in a lot of Wicklow during this period.
Nowhere escaped the rain with all places getting a dumping at some point. For instance, Malin Head which normally does well to avoid deluges when lows are southerly tracking still had a 23.2mm daily fall on the 7th June.
The 8th June under a raw northeasterly flow was unusually cold for the time of year with maximum temperatures very suppressed as rain fell for much of the south and east. Dublin Airport did not get above 10.6C all day. Other poor maxima for this day included:
Valentia, Kerry: 12.8C
Clones, Monaghan: 11.6C
Birr, Offaly: 11.5C
Glasnevin, Dublin: 10.9C
Future Junes in 1964, 1977 (especially) and 2009 would include significantly lower maximum temps across the nation but at the time, especially for Dublin, this was an exceptionally cool June day.
The rest of June 1955 continued in an unsettled vein but more traditional westerly, changeable affair rather than the southerly tracking lows of the first third. Any attempts at fine weather were very fleeting and the often sourced Atlantic air meant it was a cloudy month, a shocking contrast to the succeeding month. It is one of the cloudiest Junes on record as a matter of fact to present day. Sunshine data is very sparse however. CSO site I would usually use does not go back to 1955.
Shannon Apt: 87.5 hrs (cloudiest June on record)
Valentia: 108.2 hrs (3rd cloudiest June on record)
Dublin Apt: 112.6 hrs (2nd cloudiest June on record)
Malin Head: 124.0 hrs (5th cloudiest June on record)
The highest temp of June 1955 I can see is 22.4C at Valentia on the 17th during a brief ridge of high pressure drawing in a warmer easterly wind but this was not definitively the highest.
The poor June would soon become a very distant memory with the arrival of July 1955. Looking at the synoptic on the very first day, it looks very benign with a flat westerly flow. The Azores High is at home, low pressure to the northwest of Scotland with an Atlantic airflow over Ireland. There was some wet conditions to the north of the country, especially on the 2nd but this would be the exception and for nearly all, 90% of their July monthly rainfall occurred on the 2nd alone. The month had as little as 1-3 wet days (days with 1mm or more) for nearly all stations. Cork had only 1 or 2mm of rain fall all month.
Through the opening week, any low pressure fizzled out or cleared eastward with a ridge from the Azores building into the country. There was already good sunshine at times but it was soon to become very sunny widespread with unbroken sunshine for many day after day for almost a week.
A classic strong high pressure system right over top of the country on the 7th July with warmth building beneath due to air compression and cloud amounts decreasing.
July 1955 as mentioned was Ireland's sunniest month on record, at least in terms of absolute extremes - we've likely had sunnier for the whole nation averaged including June 1957 and May 2025. Valentia Observatory recorded 308.3 hrs of sunshine which is the all-time record monthly sunshine total on the island - this represents 219% of its average of just 140 hours for July! It is also only one of three occasions that had a 300+hr total has been achieved in Ireland, the other two were June 1959 (only 4 years later amazingly) and May 2025. It was the sunniest month on record for Dublin Airport with 305.9 hrs and Birr too though I have no sun data available for it unfortunately. Other stations such as Malin Head (213.3 hrs) and Shannon Airport (255.3 hrs) have seen sunnier months.
Shannon Airport had 24 consecutive days of 20C or more from 5th-28th July 1955 with a max of 27.6C on the 24th including official heatwave conditions from the 7th-11th July. There was no 30C recorded in July or indeed in 1955 as you'll find out later. This is likely down to a couple of reasons including the overall colder nature of sea surface temperatures back in this time, the lack of stations in operation that did not pick up on micro-climates and there was also not a lot of very warm or hot airmasses advected towards Ireland during July. Airmasses tended to be rather modest in nature with 12C at 850hPa tending to be the peak according to reanalysis whereas we've seen 850s above 20C recently in July 2022 that helped achieve 33.0C.
The Met mentions that 29C was achieved on 8th July somewhere but I do not know where and I cannot find this value. The Shannon temp I mentioned is the highest out of the limited station data available in the public domain.
The entirety of July 1955 was then dominated by Azores ridges. There was basically no break in the weather pattern for the rest of the month, remarkable. Any time the Azores ridges weakened or went east, another one just built.
Even by the final day of July, we were still under the influence of a ridge from the Azores high. July is normally a very westerly month so to see one this blocked is phenomenal to be honest.
The Atlantic was well and truly blocked off with the jet stream pushed far to the north over Iceland through July. No spectacularly high temperatures recorded but I can see many days pushing to upper 20s or touching 30C if this month's evolution were to play out in a more modern climate.
The warm, dry summery conditions from July was to continue into August 1955 too which was actually hotter than July though not nearly as sunny or as dry.
It wasn't as warm as August 1947 which until 1995 stood widely as the warmest August on record in Ireland. Nonetheless, places were still widespread over 2 degrees above their August means. Only 5 days failed to reach 20C at Shannon Airport which had a monthly mean of 17.6C - nearly 2 degrees above the modern average, never mind back then. The mean max at Birr was 22.3C which is nearly 3 degrees above average.
The month started where July had left off with an Azores ridge influencing Ireland with variable warm sunny spells. Low to mid 20s maxima
It became fresher towards the end of the first week with the ridge forcing the wind to more of a northwesterly tilt decreasing temperatures back to the mid-teens for a time and fair amounts of cloud but continuing dry.
This was temporary as more high pressure built right over top of the country. There was an interesting cooler pool aloft however in the easterly wind at first so it wasn't very warm by any means especially in the east where Dublin Airport had a disappointing max of 17C on the 10th. By the 13th it had warmed up everywhere when the air destabilised with possibly some thunderstorms but information limited.
Here's something that hadn't been seen since the end of June or start of July… a westerly flow! High pressure slipped to the south on 15th August bringing in low pressure off the North Atlantic. Some wet conditions out north and west but the heaviest falls tended to stay offshore whilst the east remained almost completely dry.
By the 19th August, the Atlantic flow was already running out of steam with high pressure building from the Azores again and to the east. This would usher in the hottest part of the summer. It doesn't look like much but the warm air and slight kinks in the isobars was enough to bring severe thunderstorms to places. Dublin Airport had a daily fall of 54.4mm on the 21st August.
Warm air advection inflated the ridge with a proper block over Scandinavia bringing in very warm southeasterly winds. Widely temperatures were reaching between 26 to 29C. The highest temperature was 29.8C at Valentia Observatory on this day 24th August 1955. This would stand as the August record for Ireland until 20 years later in 1975 and again another 20 years later in 1995 - funny how that worked out that way. It remains Valentia's highest August temperature on record to the present day.
The warm, dry weather would see us out to the end of August when it gradually became more westerly leading us into a westerly September.
That's the summer of 1955. I didn't give as much information as I would like to but unfortunately data is sparse and currently I do not have access to the newspaper archive either. But I hope you enjoyed it nonetheless and that it was an interesting enough summer to pick for a post like this.
Photography site - https://sryanbruenphoto.com/
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Highest monthly sunshine totals on record can be found below for the island. I contemplated whether to include the Magilligan, Co. Derry value from May 2025 or not as it is an estimated value converted from Kipp & Zonen sensor to Campbell-Stokes for historical comparison. Modern automated stations in the UK use K&Z sensors for sunshine recordings whereas manuals use CS, I'm not sure about the Republic as I've never seen reference to K&Z sensors at Irish stations nor any recalculated figures.
This Magilligan value is the only time I'm aware of that Northern Ireland has a higher record monthly sunshine total than the Republic. Even if not accurate or dubious, May 2025 still holds the record with 298.8 hours of sunshine at Johnstown Castle, Co. Wexford. In terms of national average, May 2025 is probably the sunniest month in Irish recording history with a MINIMUM total of 267.2 hours (Gurteen) out of 9 stations. Even in Northern Ireland, the lowest K&Z total was 259.3 hours at Thomastown, Co. Fermanagh which would likely be over 270 hours with a CS conversion. 9 stations is a very small amount but normally one or a few stations are closer to 200 hours like in May 2020 where the minimum total was 220.9 hours at Belmullet. And in July 1955, there was similar minimum totals despite both Valentia Observatory and Dublin Airport achieving over 300 hours. Basically, May 2025 was a historic sunny month.
The highest winter (December to February) seasonal total is likely 312.5 hours at Cork Airport in winter 2009-10. Whilst I cannot confirm if this is the absolute highest, it is pretty ridiculously high for a winter sunshine total in Ireland with no other record I'm aware of coming close. Dublin's sunniest winter is over 60 hours less! Given how extremely blocked winter 2009-10 was with a record negative North Atlantic Oscillation, perhaps it's no surprise it was this sunny.
The highest spring (March to May) seasonal total is probably 649.7 hours at Malin Head in spring 2025. I'd be surprised if this was beaten as spring 2025 is by far and away the sunniest spring season on record nationally with nearly all stations setting records. The highest prior to this I'm aware of is 638.2 hours at Rosslare in spring 2007.
The highest summer (June to August) seasonal total is definitely 796.8 hours at Rosslare in summer 1959. This is an average of 8.7 hours of sunshine per day, extreme for a whole season in Ireland and represents 56% of the potential sunshine which for a month would be notable but not extreme. For a whole season that is truly remarkable. There is no summer sunshine total that comes close to this even in Rosslare which unfortunately stopped recording in 2008 but was famous as the "sunny southeast". Johnstown Castle, its replacement since, doesn't catch as much sunshine. Its summer 1995 (its second sunniest summer) total is over 85 hours less than 1959. Some Irish summer months of the past haven't even recorded that much sunshine.
I am nearly certain that the highest autumn (September to November) seasonal sunshine total was 427.6 hours at Rosslare also in 1959 after the remarkably sunny summer. What a year 1959 was for sunshine with a record-breaking sunny January too earlier in the year as you'll see below.
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I attempted to do the table for the lowest monthly sunshine totals on record but unlike the highest, Northern Ireland would probably hold a good bit more records here. I have no way of converting K&Z values myself to CS equivalent as I am not aware of the difference between the values. The UK Met Office don't make them public unless in extreme scenarios such as May 2025. Then there is also the fact Northern Ireland monthly sunshine totals are in general trickier to access. The record lowest Republic sunshine total for July is 54.7 hours at Newport, Co. Mayo in July 1998 whilst Magilligan reported 52.1 hours in July 2022 but the latter is a K&Z value. This makes it impossible to do a lowest sunshine records table with the current state of the historical database for the whole island.
So here's just a few stats on a limited number of Irish stations starting off with record monthly sunshine totals for highest. There are more sunshine recording stations than this but the Met don't make their data public for whatever unknown reason.
Note Cork Airport has the unique characteristic of every month having a record of at least 100 hours. No other station currently does this but Mullingar only needs a record January of at least 4 additional hours to also achieve this. Quirky too that some stations have a higher December record than November and a higher August record than July. Things like this are why I love analysing the Irish climate as whilst its extremes may be boring on a global scale, it's full of novelties and quirks that are not what you expect.
Photography site - https://sryanbruenphoto.com/
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