The month started off warm and dry with most of the highest temperatures recorded in the first week.
However, these top temperatures were some of the lowest for May in years: Mullingar recorded its highest value of 17.3C, its lowest maximum temperature since 1972.
Rainfall was up in the west of the country with Belmullet, Co Mayo, recording its wettest May in 25 years, while Cork Airport had its wettest May in five years.
However, weather in the east and southeast remained dry for the month.
Minimum daily temperatures for the month were about 2C above average around the country.
However, this is nothing unusual, according to Ruth Coughlan of Met Éireann.
“These are natural variations. They are well within the range you would expect for spring,” she said.
Rain and wind levels for the month were varied around the country, with Met Éireann blaming the changeable weather on depressions over the Atlantic.
Sunshine levels were near average across the country with Casement Aerodrome in Dublin recording its warmest May since 2001. However, it was a dull month in the south and southwest with Valentia Observatory recording its dullest May in 20 years.
Average windspeeds were up: Malin Head had the highest mean windspeed ever recorded in May with 19.4 knots or 36km/h, while Belmullet recorded the strongest gust ever seen in May with 78 knots or 144 km/h on May 23.
In general for spring mean temperatures were above average by 1-2C across the country, making it the warmest spring since 1997.
Rainfall was below average almost everywhere with Dublin Airport recording its driest spring since 1990.
Sunshine levels were above average around the country for the season while windspeeds were about average.