Hottest Day in Ireland: 33.3°C vs 33.0°C Debate

In the summer of 2022, Phoenix Park in Dublin hit 33.0°C — close enough to shatter Ireland’s longest-standing heat record. Yet the official title of “hottest day ever” still belongs to Kilkenny Castle, where a disputed 33.3°C reading was logged on 26 June 1887. Climate scientists and Met Éireann are still arguing over which one should really count. This article walks through what the records show, why the 1887 figure is under scientific scrutiny, and what the debate means for anyone tracking Ireland’s warming climate.

All-time record: 33.3°C, 26 June 1887, Kilkenny · Recent high: 33.0°C, 18 July 2022, Phoenix Park · 20th-century peak: 32.5°C, 29 June 1976, Boora · 2016 high: 30.4°C, Mount Dillon

What is the hottest day in Ireland?

Ireland’s official highest temperature stands at 33.3°C, recorded at Kilkenny Castle on 26 June 1887. Met Éireann lists this figure as the national heat record, a benchmark that has endured for 137 years. The reading came during an extreme heat event that affected the Midlands and southwest of Ireland, with Kilkenny Castle weather station (opened in 1886) documenting 92°F — later converted to 33.3°C.

That status quo faced a serious challenge on 18 July 2022, when Phoenix Park in Dublin reached 33.0°C. According to Met Éireann, this was the highest temperature recorded in the 21st century and the hottest Dublin had ever seen. The 0.3°C gap meant it fell just short of the 1887 figure — but for climate scientists, that margin tells a complicated story.

1887 Kilkenny record

Evelyn Cusack, Head of Forecasting at Met Éireann, called the 1887 reading “sacred” — a proper temperature recorded under extreme conditions, not a clerical error. The Irish national meteorological service continues to stand by the figure, noting that the heat on 26 June 1887 was focused on the Midlands and southwest, which aligns with Kilkenny’s geographic position.

2022 Phoenix Park reading

Phoenix Park’s 33.0°C on 18 July 2022 was 12.8°C above the seasonal normal for that date, according to The Independent. The reading surpassed the previous 21st-century high of 32.3°C at Elphin, Co. Roscommon (19 July 2006) by 0.7°C. For Dublin, it was a first: no previous station in the capital had ever recorded anything that high.

Has Ireland ever hit 30 degrees?

Yes — multiple times, and the occurrences are becoming more frequent. The 30°C threshold has been breached at least a dozen times in recorded Irish meteorological history, with notable instances at Boora, Co. Offaly (32.5°C on 29 June 1976), Mount Dillon (30.4°C on 19 July 2016), and dozens of stations during the July 2022 heatwave. Met Éireann’s provisional data shows Dunsany, Co. Meath reached 30.2°C and Mullingar, Co. Westmeath hit 30.4°C during that same July 2022 event.

Historical instances above 30°C

Beyond the headline figures, Dromore Castle in Co. Kerry recorded 32.2°C on 27 June 1887, according to Pacific Climate data. Boora, Co. Offaly’s 32.5°C in 1976 remains the highest verified temperature of the 20th century. What distinguishes these readings from the Kilkenny outlier is that they align more closely with concurrent measurements at surrounding stations.

Recent exceedances

Oak Park in Co. Carlow recorded 28.8°C on 13 June 2023 — not a record, but a reminder that temperatures in the high 20s are becoming routine during Irish summers. The trend line is clear: Irish Examiner reports that Ireland is unusual among European nations in holding its national heat record from the 19th century rather than a more recent date.

Was 1976 a hot summer in Ireland?

The summer of 1976 brought a notable heatwave across the British Isles, and Ireland was not immune. Boora, Co. Offaly recorded 32.5°C on 29 June 1976, a figure that still stands as the highest verified temperature of the 20th century. The Royal Meteorological Society’s historical analysis confirms that June 1887 was exceptionally hot across Ireland with widespread drought conditions — a point of comparison that scientists use when evaluating whether the Kilkenny reading was physically plausible.

Heatwave duration

The 1976 event lasted roughly two weeks across the British Isles, with Ireland experiencing sustained temperatures in the high 20s and low 30s. Unlike the isolated Kilkenny reading of 1887, multiple stations across Ireland reported concurrent high temperatures during this period, lending the Boora record greater scientific credibility.

October 9th fog event

An unusual meteorological footnote from 1976: the same heatwave that brought summer extremes was followed by a curious fog event on 9 October. While not directly related to temperature records, this highlights the unusual character of that year’s weather patterns.

What was the hottest temperature in Ireland last 10 years?

The last decade shows a clear upward trajectory. Elphin, Co. Roscommon set a 21st-century record of 32.3°C on 19 July 2006 — which held for 16 years before 2022 shattered it. Mount Dillon reached 30.4°C in July 2016, marking the first time since the 1970s that a station came close to the 30°C mark. Then came the July 2022 event, which reset the bar entirely.

2022 record

Phoenix Park’s 33.0°C on 18 July 2022 is not just a new high for this century — it’s the highest temperature recorded anywhere in Ireland in more than a century. The Journal reports that a scientific study confirmed the 2022 reading as a significant outlier compared to historical station differences, suggesting the conditions that produced it were genuinely extraordinary by Irish standards.

Yearly highs

2023 brought a cooler summer by comparison, with Oak Park’s 28.8°C on 13 June representing the year’s peak. Still, even this figure would have been remarkable a generation ago. The data suggests that annual temperature records in Ireland are being set more frequently — and at higher values — than historical baselines would predict.

What are the top hottest days in Ireland?

A ranked list of Ireland’s highest temperatures reveals a pattern: most occurred in June or July, with stations concentrated in the Midlands and midlands-adjacent counties. The curious absence of a post-2000 record at the very top is precisely what the scientific debate centers on.

Ranked list

At number one, Kilkenny Castle (1887) at 33.3°C — though this record is contested. Second, Phoenix Park (2022) at 33.0°C — technically provisional but widely accepted. Third, Boora (1976) at 32.5°C. Fourth, Elphin (2006) at 32.3°C. Fifth, Dromore Castle (1887) at 32.2°C. The 2022 event also produced multiple station records: Mullingar (30.4°C) and Dunsany (30.2°C) both set local records that year.

Records per decade

The distribution is telling. The 1880s produced at least two days above 32°C. The 1970s added another benchmark. The 2000s and 2010s saw readings inching upward before the 2022 breakthrough. Copernicus peer review literature suggests that a formal reassessment could shift the official ranking, with Boora 1976 as a credible candidate to replace Kilkenny 1887.

Expert perspectives

“The 1887 Kilkenny Castle record is sacred — it was a proper temperature recorded during extreme heat focused on the Midlands.”

— Evelyn Cusack, Head of Forecasting, Met Éireann via Irish Examiner

“It’s physically implausible that Kilkenny could have been so different to other stations on the same day. The 1887 record is like a 100m sprint world record run from the 60m mark.”

— Prof Peter Thorne, Climate Expert, Maynooth University, via Irish Examiner

“I’m 100% certain that this contention that this week was indeed the hottest recorded date in Ireland is correct.”

— Prof Peter Thorne, Climate Expert, Maynooth University, via Irish Examiner

The expert divide reflects a genuine scientific tension: Met Éireann’s operational approach treats the 1887 record as a valid historical datum, while academic researchers applying modern reanalysis techniques argue that the evidence no longer supports Kilkenny as a reliable outlier. A Copernicus preprint from the climate research community notes that Ireland is the only European country still holding a national heat record from the 19th century.

Summary

Ireland’s heat record book may need a rewrite — or at least an asterisk. The Kilkenny Castle reading of 1887 has served as the national benchmark for 137 years, but scientific reanalysis reveals it as a statistical outlier: on 26 June 1887, Birr recorded 29.3°C and Roches Point reached 22.2°C on the same day, making a 4°C gap from Kilkenny difficult to explain without questioning measurement conditions. Meanwhile, the 2022 Phoenix Park reading of 33.0°C meets modern standards, has corroborating station data, and represents a genuinely extreme heat event. For climate scientists, the case for a reassignment is compelling. For Met Éireann, tradition and continuity carry weight. What is clear is that as Irish summers grow hotter, future exceedances of 33.3°C are increasingly likely — and when that happens, the debate over which record should stand may resolve itself.