AUGUST 2025 MUCH WARMER THAN AVERAGE AT ARMAGH, SUNNIER AND MUCH DRIER. EQUAL WARMEST SUMMER ON RECORD AT ARMAGH, DRIER THAN AVERAGE BUT WITH AVERAGE SUNSHINE
Armagh Observatory, 8th September 2025: Armagh Observatory reports that August 2025 at Armagh was much warmer than average, and sunnier and much drier than average. Taking June, July, and August together, the meteorological summer 2025 was the equal warmest on record at Armagh, shared with summer 1995, and drier than average but with about average sunshine.
With an average temperature of 17.0 degrees Celsius (62.6 Fahrenheit), shared with those of August 1983, 1955, and 2022, August 2025 was almost 2.4 C warmer than the (1796-2020) 225-year long-term average August temperature at Armagh (14.6 C) and approximately 1.5 C warmer than the most recent (1991-2020) 30-year August average (15.5 C). These four Augusts are now the equal fourth warmest Augusts on record at Armagh, following August 1995 (average temperature 18.2 C), 1947 (average August temperature 17.4 C), and 1997 (average temperature 17.1 C). The following cooler Augusts are 1976 and 1899 (both with average temperatures of 16.8 C).
Average August temperatures at Armagh have increased significantly over the last thirty years or so. The (1961-1990) 30-year August average was 14.8 C, compared with the most recent (1991-2020) 30-year average of 15.5 C, an increase of approximately 0.2 C per decade. Of the last ten Augusts at Armagh only three have lower average temperatures than 15.5 C.
The warmest day (highest maximum air temperature) was 27.9 C on the 12th, one of the three sunniest days of the month at Armagh. This was followed by 26.4 C on the 13th (the sunniest day), and 24.9 C on the 25th. The coolest day (lowest maximum air temperature) was 16.6 C on the 28th, followed by the 1st and 4th (both with 18.2 C). The highest minimum air temperature, notionally the warmest night, was 16.6 C on the 24th, followed by 15.9 C shortly after the time of observations (09:00 GMT) on the 2nd but attributed to the 3rd, and by 15.8 C, also shortly after the time of observations on the 22nd but attributed to the 23rd. The lowest minimum air temperature, or coolest night, was 8.3 C on the 21st followed by 9.1 C on the 10th, and 10.2 C on the 6th.
The monthly average of the daily maximum air temperatures was nearly 21.2 C. This is approximately 1.8 C warmer than the corresponding most recent (1991-2020) 30-year August average (19.4 C) and the ninth warmest such average on record at Armagh. Conversely, the monthly average of the daily minimum air temperatures, usually the lowest nighttime temperatures, was approximately 12.8 C. This is 1.2 C warmer than the corresponding most recent 1991-2020) 30-year August average (11.6 C) and the second warmest such average on record at Armagh, following August 1997 (corresponding average 13.3 C) and shared with 1955 and 1990.
The difference in the ranking of the monthly average daily maximum temperatures compared with that of the daily minimum temperatures can be understood as an effect of clouds: larger amounts of cloud tend to limit daily temperature maxima whilst raising lowest nighttime minima. Had this August been rather less cloudy, not only would the average temperature have been greater with the highest daily maximum temperatures boosted by strong sunshine, but the lowest nighttime temperatures would have been slightly lower owing to clearer skies at night.
The lowest grass-minimum temperature was 2.6 C on the 10th, followed by 2.9 C on the 21st and 5.1 C on the 17th. There were no frosts this August.
Unlike August 2023 and August 2024, this August 2025 was dominated by higher-than-average atmospheric pressure, leading to settled and largely dry weather conditions. Apart from a brief spell of windy weather on the 4th, caused by the passage across Scotland of the unusually deep and active summer depression named Storm Floris, the weather remained largely dry and settled until the arrival of another deep area of low pressure on the 25th associated with ex-hurricane Erin. This introduced unsettled conditions lasting to the end of the month and into early September.
The mean atmospheric pressure reduced to mean sea level this month was 1015 mbar, slightly higher than the 170-year (1851-2020) long-term August average of 1014 mbar. The highest 09:00 GMT atmospheric pressure reduced to mean sea level at Armagh was 1029.6 mbar on the 16th, and the lowest was 990.1 mbar on the 31st.
Approximately 30 gulls were observed flying in a “V” formation in a north-easterly direction on the 2nd, and swallows were recorded on the 5th. The annual Perseid meteor shower was observed on the 12th.
Raindrops, observed on the afternoon of the 25th, presaged a change in the weather to breezy, more unsettled conditions. Rainbows were recorded on the evenings of the 29th and 30th.
Total rainfall was 29.0 mm including 6 trace values, that is, 28.7 mm if trace values are ignored. This is approximately 35% of the 183-year long-term (1838-2020) average August precipitation at Armagh (82.35 mm) and 37% of the most recent (1991-2020) 30-year average (78.6 mm). August 2025 was therefore much drier than average, with just nine rain days, defined as days with precipitation of at least 0.2 mm. This was the 13th driest August on record at Armagh and the driest since the very dry August 2022 (24.9 mm). Had the pattern of weather not changed with the arrival of ex-hurricane Erin, the month would have been very dry indeed. Total precipitation during the last six days of the month amounted to 24.4 mm, nearly 85% of the monthly total.
The wettest day was the 26th, with 9.5 mm (0.37 inches) of rainfall, followed by the 31st with 5.7 mm and the 30th with 4.9 mm.
With a total of 153.6 hours of strong sunshine, August 2025 was sunnier than average, with approximately 15% more than the 140-year (1881-2020) long-term August average at Armagh (133.1 hours) and 9% more than the most recent (1991-2020) 30-year average (140.6 hours). August was the only month this summer to be sunnier than average.
Considering the three months June, July, and August together, the meteorological summer 2025 had an average temperature of 16.5 C. This was the equal warmest summer on record at Armagh, shared with summer 1995. It was also drier than average but with average sunshine. The few warmest summers at Armagh are now 2025 and 1995, both with average summer temperatures of 16.5 C, followed by 2006 (16.3 C) and then 1983, 2023, 2021, 2018, 1826 and 2013 (all approximately 16.2 C).
The average summer temperature was approximately 2.2 C warmer than the 225-year (1796-2020) long-term average summer temperature at Armagh (14.3 C) and 1.4 C warmer than the most recent (1991-2020) 30-year average (15.1 C). The three warmest days at Armagh this summer were 29.7 C (12th July), 29.3 C (20th June), and 27.9 C (12th August). There were two heatwaves (sequences of three or more days with maximum temperatures greater than or equal to 25.0 C), namely the 19th to the 21st of June and the 10th to the 13th of July.
With June wetter than average, July with roughly average precipitation, and August much drier than average, total summer precipitation (188.9 mm including 12 trace values) was less than average, supplying 86% of the 183-year (1838-1990) long-term summer average at Armagh (219.4 mm) and 89.7% of the most recent (1991-2020) 30-year average (219.4 mm). This was by no means the driest summer on record, for example the three driest summers at Armagh are 1995 (80 mm), 1983 (88 mm), and 1870 (92 mm).
Similarly, although June was slightly duller than average and July had roughly average sunshine, the slightly sunnier than average August led to summer 2025 being close to average so far as strong sunshine is concerned. The summer total of 422.6 hours of strong sunshine was approximately 99% of the 140-year (1881-2020) long-term average summer sunshine at Armagh (426.7 hours) and 101% of the most recent (1991-2020) 30-year average (420.0 hours).
These data refer to observations at Armagh Observatory, which has been recording the weather since 1795.
For further information, please contact:
Professor Mark E. Bailey
Emeritus Director of Armagh Observatory
Armagh Observatory and Planetarium
College Hill
Armagh
BT61 9DG
Tel: 028-3752-2928
E-mail: mark.bailey@armagh.ac.uk
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