Depressions over the Atlantic were the main influence on Ireland’s weather during the month of May, giving generally unsettled weather across the country with very strong winds at times.
The start of the month was relatively warm and dry, with almost all of the highest temperatures for the month recorded in the first week. These maximum temperatures were some of the lowest May maxima recorded in recent years, however; Mullingar’s highest value of only 17.3°C was its lowest for May since 1972. Minimum daily temperatures for the month were around two degrees above normal, with a number of stations recording their highest ever May daily minimum values. Overall, mean air temperatures for the month were above average everywhere, with Claremorris and Casement Aerodrome recording their warmest May since 2001.
Rainfall totals and number of wetdays(1.0mm or more) recorded for May were well above average in the western half of the country, but it was another dry month in the east and southeast. Accumulations of rainfall for 2011 so far of between 200mm and 300mm in these areas represent around 75% of normal for the five-month period. Dublin Airport recorded only 67% of its long-term average for this month and also recorded its lowest daily fall for May since 1998 of 5.7mm.
Sunshine totals were near average across the country except in the south and southwest where it was a dull month. Valentia Observatory measured its dullest May since 1981, while Shannon Airport’s highest daily sunshine of 11.5 hours was its lowest such value for May in 46 years.
Mean windspeeds for the month were all above average with several stations recording their highest mean winds for May for at least 25 years. The highest mean monthly windspeed for May ever recorded in Ireland of 19.4 knots (36km/h) was measured at Malin Head, while Belmullet measured a record-breaking May gust for Ireland of 78 knots (144km/h) on the 23rd of the month.