MAY: Very dry and sunny
Continuing from April, May was another very dry and settled month with high pressure dominating once again. The first half of the month was cool overall, with high pressure positioned to the northwest of Ireland, which kept the winds mostly between easterly and northerly. It warmed up briefly towards the end of the first week, with some thunderstorm activity on the 9th, followed by an arctic maritime air mass moving South over the country on Sunday the 10th, cooling it down again for several days. There was some rain during this period, especially in the Southwest, as Atlantic weather fronts encroached, but it stayed mostly dry elsewhere. The second half of the month was milder overall with high pressure positioned to the south or east of the country, which brought a milder air-flow from the southwest or south. The weather did break down between the 21st and 23rd, when a deep area of low pressure, containing remnants of post-tropical storm Arthur (named by the National Hurricane Centre), came close to the west coast of Ireland, while moving northeast towards the north of Scotland. This brought widespread rain, heaviest in the Southwest, and the strongest winds of the month. It settled down again from the 24th with high-pressure building from the south and drifting over Ireland towards Scandinavia, which brought a tropical continental air mass over Ireland from the southeast, keeping it mostly dry and very warm up to the end of the month.
Extreme Values at Synoptic Stations
Rainfall
Highest total: 68.8 mm at Cork Airport, Co Cork (84% of its LTA)
Lowest total: 8.3 mm at Phoenix Park, Co Dublin (14% of its LTA) (its driest May since 1991)
Highest daily rainfall: 24.2 mm at Roches Point, Co Cork (38% of its monthly LTA) on Thu 21st
Temperature
Highest mean monthly temperature: 13.0°C at Shannon Airport, Co Clare (1.0°C above its LTA)
Lowest mean monthly temperature: 10.9°C at Dublin Airport, Co Dublin (0.2°C above its LTA)
Highest Air temperature: 26.8°C at Mount Dillon, Co Roscommon (11.0°C above its LTA) on Sat 30th
Lowest air temperature: -3.2°C at both Mount Dillon, Co Roscommon on Thu 14th and Mullingar, Co Westmeath on Tue 12th (Mullingar’s lowest May temperature on record (record length 70 years))
Lowest grass minimum: -8.9°C at Mount Dillon, Co Roscommon on Thu 14th
Sunshine
Highest monthly total: 295.0 hrs (daily mean 9.52 hrs/day) at Dublin Airport, Co Dublin
Lowest monthly total: 220.9 hrs (daily mean 7.13 hrs/day) at Belmullet, Co Mayo
Highest daily sunshine: 15.3 hours at Johnstown Castle*, Co Wexford on Sun 31st
Full report <<here>>
SPRING: Very dry, especially in the east, sunny everywhere, warm for most
High pressure dominated through most of spring 2020, which led to very dry conditions, especially in the East. The first half of March saw low pressure to the north with Atlantic weather fronts crossing the country in a cool westerly airflow. Pressure rose steadily from mid-month and apart from stalled fronts giving some rain in the North and West, the second half of March was mostly dry and cool. The mainly dry and settled weather continued for most of April with drought and dry spell condi-tions reported at many locations across the country. A shift in the position of the high-pressure system to the northeast during April saw an easterly airflow off the continent dominate, which brought warmer weather overall, especially in the West. Low pressure brought rain countrywide at the end of April, which ended the drought and dry spell conditions. High pressure soon re-established control at the beginning of May, this time to the northwest of Ireland, which meant the first half of May was cool with an arctic blast coming south over the country on the 10th. The second half of May saw high-pressure develop to the south of Ireland and drift to the east, which brought warmer weather, culminating in a very warm tropical continental air mass feeding in over the country from the southeast towards the end of the month.
Extreme Values
Rainfall
Highest seasonal total: 258.4 mm at Newport, Co Mayo (78% of its LTA)
Lowest seasonal total: 52.6 mm at Phoenix Park, Co Dublin (31% of its LTA) (its driest spring on record (record length 170 years)
Highest daily rainfall: 31.0 mm at Shannon Airport, Co Clare (39% of its monthly LTA) on Mon 9th Mar
Temperature
Highest mean seasonal temperature: 10.2°C at Newport, Co Mayo (0.9°C above its LTA)
Lowest mean seasonal temperature: 8.4°C at Dublin Airport, Co Dublin (0.1 below its LTA)
Highest air temperature for the season: 26.8°C at Mount Dillon, Co Roscommon on Sat 30th May
Lowest air temperature for the season: -4.2°C at Dunsany, Co Meath on Thu 5th Mar
Lowest grass minimum for the season: -10.1°C at Mount Dillon, Co Roscommon on Fri 20th Mar
Sunshine
Highest seasonal total: 624.5 hrs (daily mean 6.79 hrs/day) at Johnstown Castle*, Co Wexford
Lowest seasonal total: 530.4 hrs (daily mean 5.77 hrs/day) at Valentia Observatory*, Co Kerry
Highest daily sunshine for the season: 15.3 hours at Johnstown Castle*, Co Wexford on Sun 31th May
Full report <<here>>