Armagh Observatory, 6th May 2023:

Armagh Observatory reports that April 2023 was warmer than average but slightly duller and wetter. The mean temperature was 9.50 degrees Celsius (49.11 Fahrenheit), approximately 1.6 C warmer than the 225-year long-term (1796–2020) April average at Armagh (7.92 C) and 0.7 C warmer than the most recent (1991–2020) 30-year average (8.80 C). This was the warmest April at Armagh for three years, that is, since the very sunny and  warm April 2020 (10.2 C).

The highest maximum air temperature or warmest day was an unremarkable 19.4 C on the 29th, the warmest day of the year so far. This was followed by 18.5 C on the 30th and 18.3 C on the 21st. The lowest maximum air temperature, notionally the coolest day, was a relatively mild 8.7 C on the 22nd. This was followed by 8.8 C, which unusually occurred around the time of the daily readings on the 13th and so, following meteorological conventions, was attributed to the 12th. The third-lowest maximum air temperature was 8.9 C on the 11th.

The highest minimum air temperature, notionally the warmest night, was 11.2 C. This occurred shortly before midnight on the 29th but following meteorological conventions is attributed to the 30th, the day the observations were taken. This was the warmest April night at Armagh for three years, that is, since 11 April 2020 (11.4 C).

This warmest night was followed by 9.5 C shortly before midnight on the 28th and therefore attributed to the 29th. This in turn was followed by 9.3 C in the small hours of the 18th.
The lowest minimum air temperature, or coolest night, was -1.1 C on the 25th followed by -0.5 C on the 14th and 0.7 C on the 7th.

There were several quite cold ground frosts among the 14 nights that recorded such frosts, that is, grass-minimum temperatures less than or equal to zero Celsius. The coldest three of these were -7.4 C on the 25th, -7.2 C on the 14th, and -6.8 C on the 15th. There were only two days, namely the 25th and 14th, with nighttime air frosts, neither of which were severe.

The 134.7 hours of strong sunshine at Armagh was approximately 10% less than both the 140-year (1881–2020) long-term April average (145.54 hours) and the most recent (1991– 2020) 30-year average (149.87 hours). This April was duller than average, the dullest April at Armagh for four years, that is, since April 2019 (108.5 hours of strong sunshine).
The three sunniest days were the 20th with 13.6 hours of strong sunshine followed by the 21st (12.2 hours) and the 18th (12.0 hours). Although this April was duller than average, the 20th was the sunniest April day at Armagh for eight years, that is, since 21st April 2015 (13.7 hours). Four of the six sunniest April days at Armagh have all occurred in the last
ten years.

Hail was reported during early afternoon on the 10th and, briefly, around midday on the 24th. A rainbow was seen late afternoon on the 10th. Three herons were observed flying east over the rookery on the 3rd.

Total rainfall was 61.45 mm (2.42 inches) including five trace values, therefore 61.2 mm if trace values are ignored. This April’s rainfall was approximately 16.5% more than the 183- year long-term (1838–2020) average April precipitation at Armagh (52.75 mm) and 10.0% more than the most recent (1991–2020) 30-year average (55.89 mm). After four drier-than-average Aprils, this was the wettest April at Armagh for five years, that is, since April 2018 (75.85 mm including five trace values).

The wettest day was the 22nd with 9.7 mm (0.38 inches) of rainfall, followed by the 11th (8.9 mm) and the 12th (8.3 mm) associated separately with the arrival and passage of Storm Noa, which on the 12th principally affected exposed southern and western coasts of Ireland and southern England.

The same storm produced an unusually low atmospheric pressure at 09:00 GMT on the 12th, namely 981.8 mb reduced to mean sea level according to the Observatory’s Kew Pattern barometer. This was the lowest 09:00 GMT April atmospheric pressure at Armagh for 24 years, that is, since 21st April 1999 (975.4 mb). The Automatic Weather Station, which records the pressure every minute, registered a 0.4 mb decrease below its 09:00 GMT reading (981.2 mb reduced to mean sea level) between 09:28 and 09:48 as the developing low-pressure area associated with Storm Noa moved rapidly eastwards.

These data refer to observations at Armagh Observatory, which has been recording the weather at Armagh since 1795.


Mark Bailey at the Armagh Observatory, College Hill, Armagh, BT61 9DG.

Tel.: 028-3752-2928;;




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