VERY WARM JULY DESPITE AVERAGE RAINFALL AND STRONG SUNSHINE
Armagh Observatory, 21st August 2025: Armagh Observatory reports that July 2025 was much warmer than average despite roughly average rainfall and nearly average sunshine. The month was the equal seventh warmest July on record at Armagh, while the four-day heatwave from the 10th to 13th of July included the hottest 12th of July ever seen in the city.
The monthly average temperature, that is, the average of the daily maximum and minimum temperatures, was 17.1 degrees Celsius (62.8 Fahrenheit). Despite only average amounts of strong sunshine, July 2025 was approximately 2.23 C warmer than the 225-year long-term (1796-2020) average at Armagh (14.87 C) and 1.38 C warmer than the most recent (1991-2020) 30-year July average (15.72 C). This was the warmest July at Armagh for four years, that is, since the very warm July 2021 (mean temperature 17.9 C), and the equal seventh warmest July on record at Armagh shared with July 1934.
230 Years of Weather Recording 14 July 2025 Armagh Observatory and Planetarium Armagh CREDIT: LiamMcArdle.com
The average of the daily maximum air temperatures was 21.06 C, approximately 1.4 C warmer than the corresponding most recent (1991-2020) 30-year July average (19.66 C). However, with very slightly less than average amounts of strong sunshine and therefore with clouds tending to cap daily maximum temperatures, this was only the sixteenth warmest such July average on record at Armagh.
The average of the daily minimum air temperatures, which is nearly the same as the mean of the lowest nighttime air temperatures, was 13.14 C. This was also approximately 1.4 C warmer than the corresponding most recent (1991-2020) 30-year July average (11.77 C) but in this case it was the second highest such average on record at Armagh, after the record-breaking July 2013 (average minimum air temperature 13.36 C). In this case, the effect of clouds was to maintain relatively mild nighttime air temperatures. Such results illustrate the key role of greater or lesser amounts of strong sunshine, and conversely of lesser or greater amounts of cloudiness, in determining an important meteorological quantity, that is, the daily temperature range. It is interesting to note that the observer recorded a cloudy or overcast sky on 27 of the 31 days of the month and estimated on 26 days that total cloud cover at the time of observations was six or more oktas.
230 Years of Weather Recording – 14th July. Showing sunshine record for hottest day 12th July 2025. Armagh Observatory and Planetarium Armagh CREDIT: LiamMcArdle.com
It is not surprising to find that the warmest day of the month, namely 29.7 C on the 12th, was also the sunniest, and the only day of the month with no clouds (zero oktas) recorded at the time of observations. With 12.9 hours of strong sunshine, this was the seventh warmest July day on record at Armagh and the hottest 12th of July. The six warmer July days at Armagh are 22 July 2021 (31.3 C), 18 July 2022 (31.2 C), 21 July 2021 (30.5 C), 10 July 1934 (30.3 C), 13 July 1983 (30.0 C), and 18 July 2006 (29.9 C). The previous warmest 12th of July at Armagh was 29.3 C on 12 July 1983.
The UK Meteorological Office defines a heat wave in Northern Ireland to be any period of at least three consecutive days when the maximum daily air temperature meets of exceeds 25.0 C (77.0 F). While this condition had been met for a three-day period beginning on the 19th of June 2025, it was met again for a four-day period beginning on the 10th of July 2025. The second heatwave of summer 2025 supplied the four warmest days of the month this year at Armagh, namely 29.7 C on the 12th, 27.6 C on the 11th, 27.3 C on the 13th, and 25.5 C on the 10th, three of which were also the sunniest. The 12th of July 2025 (maximum temperature 29.7 C) was also the warmest day of the year at Armagh, surpassing the 29.3 C previously achieved on 20 June 2025.
The coolest day or lowest maximum air temperature, was a relatively warm 16.6 C, followed by 17.3 C on the 21st and 18.1 C on the 23rd. The highest minimum air temperature, usually the warmest night, was 16.4 C on the 13th, followed by 15.9 C on the 14th and 15.3 C on the 25th. The lowest minimum air temperature, or coolest night, was 7.4 C on the 2nd, followed by 9.3 C on the 3rd and 10.0 C on the 16th. There were no air frosts or ground frosts this month, but the lowest grass-minimum temperature was 0.1 C on the 2nd, followed by 2.3 C on the 3rd and 4.1 C on the 16th.
230 Years of Weather Recording 14 July 2025 Armagh Observatory and Planetarium Armagh CREDIT: LiamMcArdle.com
Total precipitation was 71.9 mm (2.83 inches) including 4 trace values, that is, 71.7 mm if trace values are ignored. This was approximately 98% of the 183-year long-term (1838-2020) average July precipitation at Armagh (73.4 mm) and 104% of the slightly lower most recent (1991-2020) 30-year July average (69.0 mm), making total rainfall roughly average.
Only two of the last fifteen months have been significantly wetter than average at Armagh, leading to a growing concern that unless rainfall returns to normal (which eventually it always does) we may soon be entering a period of drought. The wettest day this July was the 20th with 15.3 mm (0.60 inches) of precipitation, followed by the 21st with 15.0 mm and the 17th and 18th both with 7.7 mm. However, the total rainfall on the 20th and 21st (30.3 mm) was part of the same weather event and occurred within a single 24-hour period; it was chance that it was divided almost equally across two meteorological days.
A heavy hail shower that occurred during early afternoon on the 2nd was noteworthy for the size of its hailstones (up to 9mm across) and the observation of rising water vapour as they later melted. Thunder was heard in the early hours of the 14th, and again around midday the same day.
A pair of hooded crows was observed robustly chasing off a buzzard near the weather station on the morning of the 3rd, and around the time of observations on the 7th another was seen mobbing a buzzard. The rarely observed behaviour of a thrush ‘anting’ was seen during late morning of the 9th. This is when a bird rubs ants or other insects over its body, possibly as a form of parasite control. A further rare observation was the pair of jays seen near the weather station around the time of observations on the 27th and, around midday on the 31st, the first sighting of a peacock butterfly.
This month there was a roughly average amount of strong sunshine, the total of 134.2 hours representing nearly 99% of the 140-year long-term (1881-2020) July average at Armagh (135.9 hours) and almost 100% of the most recent (1991-2020) 30-year July average (134.8 hours). This was the fourth July in a row at Armagh that has not been sunnier than average. The sunniest day was the 12th with 12.9 hours of strong sunshine, followed by the 11th with 12.6 hours, and the 13th with 12.1 hours.
These data refer to observations at Armagh Observatory, which has been recording the weather at Armagh 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