Precipitation

An increase in seasonality in precipitation can be expected with significant decreases projected for spring and summer and increases for winter.

An increase in the occurrence of extreme rainfall events is likely.

For Ireland, when compared with an annual average rainfall of 1186mm for the period 1961-1990, the thirty year period 1991-2020 shows a 7% increase in rainfall.
Over Ireland, the decade from 2006-2015 was the wettest in the period 1711-2016.
There is evidence of an increasing trend in winter rainfall and a decrease in summer rainfall, but there can be high variability in precipitation amounts over space and time.

Projections of precipitation indicate that precipitation is expected to become more variable, with substantial projected increases in the occurrence of both dry periods and heavy precipitation events, however, it is much more challenging to project changes in precipitation than temperature.
For Ireland, projected changes in the frequency of very wet days (>30mm of precipitation) indicate a marked increase with mean values of 21% and 31% for the RCP 4.5 and RCP 8.5 scenarios, respectively. The largest increases are noted for Autumn and Winter.
Extreme precipitation events are projected to become more frequent, with changes in rarer 50-year events being more marked than 10- and 20-year return periods. Under the Late action scenario, the annual maximum daily rainfall that used to occur once every 50 years, on average, will become approximately twice as frequent.