Armagh Observatory reports that May 2022 was warmer, duller and slightly wetter than average.  Taking March, April and May together, the meteorological spring was warmer, sunnier, and drier than average.

The observed mean temperature was 12.75 degrees Celsius (54.9 Fahrenheit).  However, owing to a slowly increasing error in the alcohol minimum thermometer, which was discovered and corrected on 17th May, the revised mean temperature for the month was approximately 12.85 C.  This is approximately 2.2 C warmer than the 225-year long-term (1796-2020) monthly average temperature for May at Armagh (10.62 C) and 1.4 C warmer than the most recent (1991-2020) 30-year monthly May average (11.42 C).

This May was the warmest at Armagh for four years, that is, since May 2018 (mean temperature 12.9 C), and one of the top ten warmest Mays in an instrumental record of daily temperature measurements that began at Armagh around 1795.  Although questions may reasonably be raised about the accuracy of the Observatory’s earliest temperature measurements, the ten warmest Mays in Armagh’s record of monthly average temperatures are now 1809 (approximately 13.8 C), 1848, 2017 and 2008 (approximately 13.2 C), 1815 and 1808 (both approximately 13.0 C), 2018 and 2022 (both 12.9 C), 1960 (12.8 C) and 1970 (12.7 C).

The fact that May 2022 was one of the warmest Mays on record at Armagh may come as a surprise.  There were no remarkably hot days or nights, and few people think of the month as being one of great warmth.  The explanation appears to be that most days, and especially nights, were warmer than average.  In particular, the mean minimum temperature was a record high for Armagh, namely 8.74 C (or approximately 8.9 C after correcting the error in the minimum thermometer).  This is nearly 2 degrees warmer than the most recent (1991-2020) 30-year average minimum temperature for May at Armagh (7.0 C) and approximately 0.4 C warmer than the earlier record (8.5 C) set in May 1999.

The warmest average May minimum daily temperatures at Armagh are now 2022 (8.9 C), 1999 and 1970 (both 8.5 C), 2014 (8.3 C), and 1893, 2011, 1848, and 1964 (all 8.2 C).  By contrast, the average of the maximum temperatures this May was 16.8 C, also much higher than the corresponding most recent 30-year average (15.8 C) but ranking much lower (equal 20th) in the list of highest mean maximum May temperatures.

The warmest day (highest maximum air temperature) was 20.7 C on the 16th, followed by 19.4 C on both the 8th and 15th.  The 16th, with an unremarkable maximum temperature of 20.7 C, was (and has remained into at least early June) the warmest day of the year.  The coolest days (lowest maximum air temperature) were 13.4 C on the 12th, followed by 13.5 C on the 30th and 14.1 C on the 31st.

The highest minimum air temperature, which loosely corresponds to the warmest night, was an unremarkable 12.1 C on the 22nd, and the lowest minimum air temperature or coolest night was approximately 3.6 C on the 29th.

There were 3 nights with ground frost, that is, during which the minimum grass temperature fell to less than or equal to zero, the three coolest of which were -2.9 C on the 29th, and -1.6 C on both the 28th and 31st.  There were no air frosts this month.

Total May precipitation was 64.85 mm (2.55 inches) including 3 trace values (i.e., 64.7 mm if trace values are ignored).  This is approximately 11% more than both the 183-year long-term (1838-2020) average May precipitation at Armagh (58.55 mm) and the most recent (1991-2020) 30-year average (58.20 mm).  The wettest day was the 17th with 17.0 mm (0.70 inches) of rainfall, followed by the 6th with 7.5 mm.

Distant thunder was reported on the afternoon of the 16th, and also lightning.  A brief heavy rain shower occurred during early evening on the 18th, and a heavy shower of hail and rain on the afternoon of the 20th. The first sighting of swallows in the Observatory demesne occurred on the 1st and of swifts on the 9th.

May 2022 was slightly duller than average, providing a total of just 155.0 hours of strong sunshine at Armagh.  This is approximately 88% of the 140-year long-term (1881-2020) average May sunshine at Armagh (175.6 hours) and 87% of the most recent (1991-2020) 30-year average (178.8 hours).  The sunniest day was the 14th with 11.8 hours of strong sunshine, followed by 10.3 hours on the 10th and 10.1 hours on the 8th.

Taking the three months March, April and May together, the meteorological spring was warmer, sunnier and drier than average. The mean spring temperature (nearly 9.9 C) was almost 1.8 C warmer than the 225-year long-term (1796-2020) average spring temperature at Armagh (8.12 C) and approximately 0.9 C warmer than the most recent (1991-2020) 30-year spring average (8.99 C).


With March and April both drier than average, and May only slightly wetter than average, 2022 spring was drier than average at Armagh. Total spring precipitation was 148.85 mm (5.86 inches) including 7 trace values, that is, 148.5 mm if trace values are ignored.  This is approximately 89% of the 183-year long-term (1838-2020) spring precipitation at Armagh (167.0 mm) and 86% of the most-recent (1991-2020) 30-year average (173.8 mm).

The sunniest March on record at Armagh (188.4 hours of strong sunshine) and a sunnier than average April (164.7 hours) followed by a slightly duller May 2022 (155.0 hours) together produced a rather sunnier than average meteorological spring. The total of 508.1 hours of strong sunshine was approximately 120% of the 140-year long-term (1881-2020) spring average at Armagh (422.9 hours) and nearly 118% of the most recent (1991-2020) 30-year average (431.6 hours), making spring 2022 the 11th-sunniest spring on record at Armagh.

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


BT61 9DG

Tel: 028-3752-2928

E-mail: mark.bailey@armagh.ac.uk


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