Armagh Observatory reports that August 2024 was drier and sunnier than average with roughly average temperature for August. Taking June, July and August together, the meteorological summer was cooler, drier, and slightly duller than average.
With an average temperature of 15.46 degrees Celsius (59.8 Fahrenheit) August 2024 was 0.83 C warmer than the (1796-2020) 225-year long-term average August temperature at Armagh (14.63 C) and approximately 0.03 C cooler than the most recent (1991-2020) 30-year August average (15.48 C). This was the coolest August at Armagh for six years, that is, since an average temperature of 15.38 C was found for August 2018.
The highest maximum temperature, or warmest day, was an unremarkable 22.8 C on the 11th, followed by 22.3 C on the 1st, and 21.6 C on the 10th. The warmest day this August was cooler than the warmest day of July (24.3 C on the 19th of July) and cooler also than the warmest day of June (24.8 C on the 24th of June). Unusually for a date so early in the year (and as occurred last year) the 24th of June 2024 has remained the hottest day of the year.
The lowest maximum temperature, usually the coolest day, was 15.6 C on the 20th followed by 16.2 C on the 25th and 16.3 C on the 22nd. The highest minimum temperature, usually the warmest night, was 16.2 C on the 2nd, followed by 15.4 C on the 12th and 15.3 C on the 13th. The lowest minimum temperature, usually the coolest night, was 5.1 C on the 31st, followed by 7.1 C on the 30th and 8.2 C on the 14th.
The lowest grass-minimum temperature was -0.9 C on the 31st, followed by 0.0 C on the 30th and 1.3 C on the 14th. There were therefore two ground frosts this month, that is, with grass-minimum temperatures less than or equal to zero Celsius.
August was largely dominated by relatively low atmospheric pressure (for August). The mean monthly pressure reduced to mean sea level was approximately 1009 mbar, compared to the 170-year (1851–2020) long-term August average of 1014 mbar. This was the lowest average atmospheric pressure for August at Armagh for 16 years, that is, since August 2008 (1007 mbar). The highest daily pressure observed at 09:00 GMT was approximately 1025 mbar on the 31st and the lowest was 999 mbar on the 23rd, associated with the passage of Storm Lillian.
Total August precipitation was 64.4 mm (2.54 inches) including six trace values, that is, 64.1 mm if trace values are ignored. This is 78% of the 183-year long-term (1838-2020) average August precipitation at Armagh (82.35 mm) and nearly 82% of the most recent (1991-2020) 30-year average (78.62 mm). This August was therefore drier than average, the driest August at Armagh for two years, that is, since the exceptionally dry August 2022 (24.9 mm including two trace values). There were no very wet days this month but 19 days with measurable precipitation greater than or equal to 0.2 mm.
The wettest day was the 22nd, with 13.7 mm (0.54 inches) of precipitation, followed by the 8th with 9.6 mm, and the 14th with 5.8 mm. The high rainfall on the 22nd was associated with the passage of Storm Lillian, the 14th and last-named storm to have affected Northern Ireland to a greater or lesser extent during the 2023/2024 storm season, and the 12th to have been named by Met Eireann, the UK Meteorological Office, and the Royal Netherlands Meteorological Institute (KNMI).
Thunder was heard during early morning of the 11th. Although heavy showers and an impressive double rainbow with supernumerary bows below was reported from near Ballygawley, Co. Tyrone, around 17:25 GMT on the 28th, no rainbows were recorded as being seen from Armagh this month.
Perseid meteors were seen from near the Observatory on the evening of the 12th, the maximum of the annual Perseid meteor shower associated with debris from Comet Swift-Tuttle. An aurora was also seen that evening around 22:30 GMT.
A speckled brown butterfly was seen near the weather station on the morning of the 6th. At about the same time, a gull was seen chasing off a buzzard. Similarly, a crow was seen chasing a kestrel on the morning of the 16th. Rooks were spooked by a heron flying overhead on the morning of the 24th. A murder of two to three hundred crows were seen swirling above the Observatory grounds on the evening of the 26th.
There were 160.7 hours of strong sunshine this August, approximately 21% more than the 140-year (1881-2020) long-term August average number of hours of strong sunshine at Armagh (133.1 hours) and 14% more than the most recent (1991-2020) 30-year average (140.6 hours). This August was therefore sunnier than average at Armagh. The three sunniest days were 11.3 hours on the 17th, followed by 9.6 hours on the 8th and 8.7 hours on the 11th.
Taking the three months June, July and August together, the meteorological summer was cooler than average, the coolest summer at Armagh for nine years, and drier and duller than average.
The mean summer temperature was 14.69 C (58.4 F), approximately 0.37 C warmer than the 225-year (1796-2020) long-term average summer temperature at Armagh (14.32 C) and 0.41 C cooler than the most recent (1991-2020) 30-year average (15.10 C). This summer had the same average temperature as that normally experienced at Armagh approximately 50 years ago, when the (1961-1990) 30-year average summer temperature at Armagh was 14.56 C. This year, the three warmest summer days at Armagh were 24.8 C (24th June), 24.3 C (19th July), and 22.8 C (11th August).
Each of the three summer months were drier than average, so summer 2024 at Armagh, with a total precipitation of 151.55 mm including 15 trace values, was also drier than average. This was the driest summer at Armagh for two years, that is, since the very dry summer 2022 (104.2 mm). Despite this, there were no very hot days, nor long dry spells. Daily rainfall totals greater than or equal to 0.2 mm occurred on 53 of the 92 possible summer days.
Whereas June and July were duller than average, August was sunnier. The three months together gave a total of 402.7 hours of strong sunshine, approximately 94% of the 140-year (1881-1990) long-term average at Armagh and 96% of the most recent (1991-2020) 30-year average. This was the dullest summer at Armagh for four years, that is, since summer 2020 (294.1 hours of strong sunshine).
In summary, it was probably the frequency of light rainfall this summer combined with lower-than-average summer temperatures and the lack of strong sunshine that together have led to the often-expressed opinion that 2024 was a generally poor summer.
These data refer to observations at Armagh Observatory, which has been recording the weather since 1795.
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