DECEMBER 2024 DRIER AND MUCH WARMER AND DULLER THAN AVERAGE. CALENDAR YEAR 2O24 MUCH WARMER AND DRIER THAN AVERAGE, AND SLIGHTLY DULLER.
Armagh Observatory reports that December 2024 was drier and much warmer and duller than average. The average December temperature was 7.0 C (44.7 F), approximately 2.4 C warmer than the 225-year (1796-2020) long-term December average at Armagh (4.64 C) and 1.8 C warmer than the most recent (1991-2020) 30-year average (5.23 C).
Calendar year 2024, with an average temperature of 10.52 degrees Celsius (50.9 Fahrenheit), was much warmer than average, and much drier and slightly duller than average. Apart from January and the four months June to September, every month was warmer and some much warmer than the corresponding most recent (1991-2020) 30-year averages, leading to 2024 being much warmer than average. This was the fourth warmest calendar year on record at Armagh in a 231-year-long daily temperature series beginning in December 1794. The six warmest years at Armagh are now 2023 (11.1 C), 2022 (10.8 C), 2007 (10.6 C), and 2024, 2021 and 2006 (all approximately 10.5 C).
This December the highest maximum air temperature, usually the warmest day, was a very mild 14.2 C occurring late evening on the 17th. This was followed by 12.7 C and 12.6 C on the afternoon of the 1st and 24th respectively. Christmas Day was a mild 12.0 C, the warmest Christmas Day at Armagh for eight years, that is, since the 25th of December 2016 (13.3 C). New Year’s Eve (31st December 2024) was also relatively mild, with a maximum temperature of 11.8 C. The turn of the year saw a change to much colder conditions with a maximum temperature of 7.1 C on the 1st of January, 3.5 C on the 2nd, and much lower temperatures later that week and into the second week of January.
The lowest maximum air temperature this December, usually the coolest day, was 3.6 C on the afternoon of the 10th, followed by 4.5 C and 5.5 C on the 11th and 13th respectively. The four days from the 10th to the 13th, with an average maximum temperature of just 4.8 C, was the coolest period in what otherwise was a very mild month with an average maximum temperature of 9.6 C.
These cold days were associated with high atmospheric pressure, which at the time of observations (09:00 GMT) on the 9th reached 1043.5 mbar reduced to mean sea level. This was the sixth highest 09:00 GMT December atmospheric pressure at Armagh and the highest December pressure for 19 years, that is, since 1044.4 mbar on 12th December 2005.
The two highest minimum air temperatures, usually the warmest nights, were 10.4 C on the 1st and 10.2 C on the 25th. These mild nights were followed by a minimum air temperature of 9.8 C on the evening of the 30th, though attributed following normal meteorological conventions to the 31st.
The lowest minimum air temperature, usually the coldest night, was -2.9 C on the early morning of the 10th. This was followed by -2.4 C on the morning of the 3rd and then by -1.1 C shortly after the time of observations on the 3rd and therefore assigned to the 4th. The average minimum air temperature this month was 4.5 C, approximately 2.1 C above the corresponding most recent (1991-2020) 30-year average (2.4 C).
This December there were 11 ground frosts, that is, days when the grass-minimum temperature was less than or equal to zero Celsius. The coldest three of these were -8.0 C on the 10th, -7.6 C on the 3rd, and -7.0 C on the 9th. There were four air frosts, those previously mentioned (-2.9 C, -2.4 C, and -1.1 C) and -0.6 C on the 9th.
Total precipitation this December was 43.8 mm (1.72 inches) including 10 trace values, therefore 43.3 mm if trace values are ignored. This is approximately 56% of the 183-year long-term (1838-2020) average December precipitation at Armagh and 54% of the most recent (1991-2020) 30-year average (81.4 mm). This was the driest December at Armagh for 14 years, that is, since the very cold December 2010 (37.95 mm including 5 trace values).
The wettest day was the 6th, with 16.0 mm (0.63 inches) of precipitation associated with the arrival and passage of a rapidly moving depression called storm Darragh, the fourth named storm of the 2024/2025 season. This gave heavy rain and strong winds reaching gale force at Armagh in the small hours of Saturday 7th December. Strong winds continued at Armagh all that day and into Sunday 9th December, causing tree damage in the Observatory grounds and power outages across Northern Ireland and farther afield. The second wettest day was 7.2 mm on the 31st, accompanied by strong winds approaching gale force. This was followed by 6.5 mm on the 5th.
Snow and sleet were observed on the morning of the 19th, and a rainbow was seen on the afternoon of the 20th.
With a total of 29.2 hours of strong sunshine, approximately 77% of the 140-year long-term (1881-2020) average for December at Armagh (38.0 hours) and 68% of the most recent (1991-2020) 30-year average (43.1 mm), December 2024 was much duller than average. This was the dullest December at Armagh for three years, that is, since December 2021 (27.8 hours of strong sunshine).
Calendar year 2024 was much drier, much warmer, and slightly duller than average. With a mean annual temperature of 10.52 C, it was approximately 1.4 C warmer than the long-term (1796-2020) average at Armagh (9.10 C) and nearly 0.6 C warmer than the most recent (1990-2020) 30-year average (9.94 C). It was also nearly 1.6 C above the conventional (1850-1900) pre-industrial baseline (approximately 8.95 C at Armagh) often used to compare current and pre-industrial temperature anomalies. 2024 was the fourth warmest calendar year on record at Armagh.
Total precipitation was 653.85 mm including 73 trace values, or 650.2 mm if trace values are ignored. This is approximately 80% of the 183-year (1838-2020) long-term annual average at Armagh (816 mm) and 79% of the most recent (1991-2020) 30-year average (825 mm). This was the twelfth driest calendar year on record at Armagh and the driest calendar year for 23 years, that is, since 2001 (total precipitation 647.45 mm including 13 trace values).
There were 1214.1 hours of strong sunshine this year, making 2024 slightly duller than average with approximately 96% of the 140-year (1881-2020) long-term average at Armagh (1261.6 hours) and 95% of the most recent (1991-2020) 30-year average (1281.2 hours).
These data refer to observations at Armagh Observatory, which has been recording the weather at Armagh since 1795.
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