Armagh Observatory reports that April 2021 was drier and sunnier than average at Armagh, but much cooler. It was the seventh driest April at Armagh since daily records of precipitation began in 1838, and the driest for four years. Although the total number of hours of strong sunshine nearly equaled that during the exceptionally sunny April 2020, this year’s April was much cooler.
Total precipitation was 12.3 mm (0.48 inches) including 2 trace values (that is, 12.2 mm if trace values are ignored). This is less than a quarter of the 183-year long-term (1838–2020) average April precipitation at Armagh (52.8 mm) and just over a fifth of the most recent (1991–2020) 30-year April average (55.9 mm). The wettest day was the 29th, with 2.5 mm (0.10 inches) of rainfall, followed by the 8th with 2.1mm.

The mean monthly temperature was 7.4 degrees Celsius (45.4 Fahrenheit), which is approximately 0.5 C cooler than the 225-year long-term (1796–2020) average April temperature at Armagh (7.9 C) and 1.4 C cooler than the most recent (1991–2020) 30-year April average (8.8 C). This was the coolest April at Armagh for five years, that is, since April 2016 (7.0 C).
This April was unusual in being cooler than the previous month (March), an event that occurs on average only once every ten or twenty years in the long-term Armagh record. It was also unusual in having a pattern of weather dominated by areas of high pressure and with few if any periods of traditional April showers. Snowflakes or snow pellets were observed on the 5th, 6th and 11th, and hail on the 9th.

The warmest day (highest maximum air temperature) was 18.6 C on the 24th, which was the warmest day of the year to date. This warmest April day was followed by 17.6 C on the 26th. The lowest maximum air temperature was 6.6 C, which occurred during late evening of the 5th, followed by 8.4 C during late evening of the 6th.
The highest minimum air temperature was 7.0 C, recorded during early morning of the 27th, followed by 6.7 C on the 19th. The lowest minimum air temperature was minus 2.5 C, a value that occurred during early morning on both the 10th and 11th.
There were several quite sharp ground frosts among the 24 nights with recorded ground frosts (minimum grass temperature less than or equal to zero), the coldest three of which were -11.5 C on the 10th, -10.6 C on the 11th and -8.5 C on the 23rd.
There were five days with nighttime air frosts.

This April was exceptionally sunny, with nearly the same number of hours of strong sunshine as in April 2020, that is, 210.5 hours compared to 213.7 hours, making April 2021 the third sunniest April at Armagh since sunshine records began at the Observatory around 1881. This April was approximately 40% sunnier than the most recent (1991–2020) 30-year average (149.9 hours).
The sunniest day was the 24th with 12.7 hours of strong sunshine, followed by the 2nd with 11.9 hours.

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;

FAX: 028-3752-7174;


URL: http://climate.armagh.ac.uk/.


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