Mild and wet first half, drier and cooler second half
The first half of January was mild, wet and often windy with Atlantic low pressure systems to the west and northwest steering numerous weather fronts across the country. The second half of the month was much drier, especially in the East, with high pressure dominating. The first two weeks of the month saw widespread rain or showers on most days. A particularly deep area of low pressure to the west of Ireland steered an active weather front across the country on the 6th, followed by heavy thundery showers on the 7th. There was a very wet and windy period between the 10th and 13th where several frontal troughs brought widespread heavy rain across the country from the southwest and west. The beginning of the third week saw an Arctic air mass move down from the north as high pressure built to the west over the Atlantic. The north to north-westerly airflow brought bands of heavy showers, falling as hail, sleet or snow in many places, between the 16th and 19th. There was widespread frost at night, with lying snow in parts of the North, West, South-west and Midlands. The Atlantic high pressure sank south, which allowed mild air to move in from the west on the 20th. The remainder of the month was relatively mild and dry with high pressure to the south and east dominating. Several weak weather fronts crossed the country during this period but rainfall amounts stayed low.
Rainfall: Below average in most places, wettest in the Southwest
The majority of monthly rainfall totals across the country were below their 1981-2010 Long-Term Average (LTA). Percentage of monthly rainfall values ranged from 65% (monthly rainfall total of 42.4 mm) at Phoenix Park, Co Dublin to 125% (monthly rainfall total of 166.4 mm) at Sherkin Island, Co Cork. Monthly rainfall totals ranged from 41.4 mm (66% of its LTA) at Dublin Airport, Co Dublin to 196.6 mm (113% of its LTA) at Valentia Observatory, Co Kerry. The highest daily rainfall total was 28.4 mm at Newport, Co Mayo on Tuesday 10th. The number of rain days ranged from 16 days at Casement Aer-odrome, Co Dublin to 29 days at both Newport, Co Mayo and Belmullet, Co Mayo. The number of wet days1 ranged from 10 days at Phoenix Park, Co Dublin to 26 days at Valentia Observatory, Co Kerry. The number of very wet days3 ranged from zero days at Phoenix Park, Co Dublin to 8 days at Valentia Observatory, Co Kerry. Three stations, Phoenix Park, Dublin Airport and Dunsany, Co Meath, had dry spells6 between 15th and 30th January lasting 16 days.
Temperature: Above average everywhere
All mean air temperatures across the country were above their LTA for the month. Deviations from mean air temperature for the month ranged from 0.1°C (7.6 °C mean temperature) at Sherkin Island, Co Cork to 1.3 °C (6.2 °C mean temperature) at Phoenix Park, Co Dublin. Mean temperatures for the month ranged from 5.0 °C (1.0 °C above its LTA) at Knock Airport, Co Mayo to 7.7 °C (0.4 °C above its LTA) at Valentia Observatory, Co Kerry. The month’s lowest temperatures were recorded on Tuesday 17th with the lowest air minimum reported at Mount Dillon, Co Roscommon with a temperature of -7.0 °C and the lowest grass minimum reported at Ballyhaise, Co Cavan with -11.7 °C. The highest maximum was reported on Tuesday 10th at Phoenix Park, Co Dublin with a temperature of 13.8 °C. All stations reported air and ground frost during the month. The number of days with ground frost ranged from 5 days at Belmullet, Co Mayo to 18 days at Markree, Co Sligo. The number of days with air frost ranged from 1 day at Sherkin Island, Co Cork to 8 days at both Mount Dillon, Co Roscommon and Claremorris, Co Mayo.
Sunshine: Sunniest in the East
Nearly all available sunshine totals were above their LTA. Percentage of monthly sunshine values ranged from 98% (monthly sunshine total of 50.0 hours) at Shannon Airport, Co Clare to 131% (monthly sunshine total of 71.0 hours) at Casement Aerodrome, Co Dublin. Monthly sunshine totals ranged from 29.6 hours (No LTA comparison*) at Belmullet, Co Mayo to 90.1 hours (No LTA comparison*) at Dublin Airport, Co Dublin. The highest number of daily sunshine hours recorded this month was 7.2 hours at Johnstown Castle, Co Wexford on Wednesday 18th. The number of dull days2 ranged from 10 days at a few stations to 16 days at both Valentia Observatory, Co Kerry and Belmullet, Co Mayo.
Wind: Storm force winds reported
Monthly mean wind speeds ranged from 5.9 knots (10.9 km/h) at Moore Park, Co Cork to 17.3 knots (32.0 km/h) at Malin Head, Co Donegal. Gales were reported on 14 days with up to strong gales reported on Saturday 7th, Wednesday 11th, Saturday 14th and Sunday 15th. Storm force winds were reported on Thursday 12th. The number of days with gales ranged from zero days at Dublin Airport, Co Dublin to 10 days at both Mace Head, Co Galway and Malin Head, Co Donegal. The number of days with up to strong gales ranged from zero days at most stations to 3 days at both Mace Head, Co Galway and Malin Head, Co Donegal. The number of days with storm force winds was one day Mace Head, Co Galway. Both the month’s highest gust and 10-minute mean wind speed was reported at Mace Head, Co Galway on Thursday 12th. The highest gust was 66 knots (122 km/h) while the month’s highest 10-minute mean wind speed was 48 knots (89 km/h).
The full report is available here
Recent Januarys in Ireland:
- 2016: Nearly all stations reported above their Long-Term Average (LTA) for rainfall and all stations reported slightly above LTA mean temperatures. Storm Gertrude brought storm-force winds.
- 2017: Rainfall totals were below their LTA while mean air temperatures were above and sunshine totals were variable.
- 2018: Rainfall totals were above their LTA everywhere. The majority of mean air temperatures were above average and all available sunshine totals were above average. Storm Eleanor brought violent Storm-force winds, storm Fionn brought storm-force winds, while storm David and Georgina brought gales.
- 2019: All monthly rainfall totals were below their LTA. Nearly all mean air temperatures were above average, while most stations had above-average sunshine totals.
- 2020: Nearly all rainfall totals were below average. All mean temperatures were above average and most stations were above average for sunshine totals. Storm-force winds were reported during Storm Brendan.
- 2021: The majority of monthly rainfall totals were above average with Storm Christoph bringing widespread rain. All mean air temperatures were below average and sunshine totals were above.