Rainfall Climate of Ireland

Rainfall is a key indicator of changes in the climate, measurements and analysis of rainfall are essential for assessing the effects of climate change on the water cycle, water balance and for flood mitigation.

The value of high quality observations to the meteorological and climatological scientific communities cannot be overstated. Historical observations are of particular value since an observation once made in time cannot be retaken, and if observations are not taken we have no way of directly knowing what the past weather and climate were like. The history of organised weather observations in Ireland goes back to the late 1700s with Observatories in Dunsink (1787) and Armagh (1790). In the first half of the 19th century readings were taken at Birr Castle (1845), Markree Castle (1824), the Phoenix Park (1829) and Trinity College, Dublin (1838). From the mid 19th century the number of stations increased and some standardisation of observations took places in line with international developments. By the early 20th century there were over 100 locations measuring rainfall, by the time the Irish Meteorological Service was formed in 1936 the number of rain gauges was over 200. Since then the network has expanded further, there are now just under 500 rain gauge locations in the country.

From these rain gauges, Met Éireann has recorded and stored nearly 9.5 million individual hourly rainfall measurements into the National Climate Database between 1939 and 2017. From this observational dataset, and others, analysis is completed to give details of the Rainfall Climate of Ireland. For example, the general impression is that it rains quite a lot of the time in Ireland, but only one out of five hourly observations will report measurable rainfall. However, there is variation between sites of course, for example at stations on higher ground (that is, highest in counties Kerry and Wicklow), rainfall is recorded every one in 3.5 to 4 hours.