Parts of the country weathered the wettest December in 130 years, official statistics from Met Éireann reveal.
As communities across the country battle to recover from Storm Frank, the new figures reveal just how much rainfall the nation endured in 2015, most notably in December.
Malin Head Weather Station in Donegal last month recorded its wettest December since 1885, and its wettest day for any month since 1955.
However, it also recorded its highest December temperature in 60 years as the country experienced an exceptionally mild month.
December rainfall was double, or even triple, its usual monthly amount in most areas.
As Storm Desmond raged, nearly 81mm fell at Malin Head in Donegal during one 24-hour period alone, marking the dampest day at Ireland's most northerly point since 1955.
And Roche's Point, near Cork city, had an extremely wet month with 340.6mm of rain, its highest rainfall for December since 1955.
The wettest days were December 3, 5 and 12, which largely coincided with the onslaught of Storm Desmond.
The statistics for December were the final chapter in a year that was dominated by wet and windy weather.
Drenched by almost 2079mm of rain in total, Mayo's principal weather station recorded its highest annual rainfall since the site opened in 1960.
Other stations in the west, south and midlands also reported their wettest 12 months in up to 14 years.
According to the national meteorological service, a 'wet day' is a day with 1mm or more of rain.
As well as being one of the wettest years on record, the report - based on preliminary data from Met Éireann's 25 principal weather stations - showed how 2015 was one of the coolest.
Temperatures were below the long-term average (LTA) mean almost everywhere.
Sligo was the chilliest county with an annual mean temperature of 8.8°C, its coolest in five years, while with an annual mean temperature of 9.9°C, Dublin was the warmest.
Temperatures plummeted to -7.9°C at Dublin Airport on February 3, making it the coldest February in almost 50 years and coldest year since 2010.
Conversely, on June 30, temperatures at the Phoenix Park soared to 25.6°C, its highest in almost two decades.