Ireland's climate explained
Why Ireland is mild, damp and changeable, and what a typical year looks like for temperature, rain, sunshine and wind.
Ireland sits between 51° and 55° north, the same latitude as Labrador and Newfoundland, yet Dublin's January is some 20 degrees milder than St John's. The difference is the Atlantic. The North Atlantic Drift, the tail of the Gulf Stream, carries warm water past the west coast all year, and the prevailing south-westerly winds blow across it before they reach land. The result is a climate with no extremes: cool summers, mild winters, rain in every month and weather that rarely stays the same for long.
Temperature
January and February are the coldest months, with average temperatures of 4 to 7°C. July and August are the warmest, averaging 14 to 16°C, with afternoons of 17 to 18°C on the coast and 19 to 20°C inland. The warmest spot over the year is Valentia Island in Kerry, with an annual average of about 10.9°C; the coolest lowland station is Mullingar at about 9.3°C. The coast is milder in winter and cooler in summer than the midlands, which is why Kilkenny records more than 50 air frosts a year and Roches Point near Cork only about 7.
Snow falls somewhere in Ireland most winters but rarely lies for long at low levels. Clones in Monaghan sees snow or sleet falling on about 18 days a year, Valentia on 6. The Wicklow Mountains can have 50 or more days with snow. The record high is 33.3°C at Kilkenny Castle on 26 June 1887, and the highest since 1900 is 33.0°C at Phoenix Park, Dublin, on 18 July 2022. The record low is −19.1°C at Markree Castle, Sligo, in January 1881. You can see all of them on the records page.
Rain
Ireland is wet, but mostly in the sense that it rains often rather than hard. The eastern half of the country gets 750 to 1,000 mm a year, the west 1,000 to 1,250 mm, and the mountains of Kerry, west Galway and Donegal more than 2,000 mm, with the wettest slopes near 3,000 mm. Dublin Airport has about 128 days a year with 1 mm of rain or more; Belmullet in Mayo has 193. A typical shower delivers a millimetre or two. The days that matter are the ones with a slow-moving front, when 20 or 30 mm falls, and the rare autumn deluge: the wettest day on record is 243.5 mm at Cloone Lake in Kerry on 18 September 1993.
October to January are the wettest months almost everywhere. April to June are the driest, and in the east February is often dry too. The county rainfall tables show the month-by-month figures for every county, and the records page ranks the counties from wettest to driest.
Sunshine
Ireland averages 3¼ to 3¾ hours of sunshine a day over the year, between about 1,100 hours in the cloudiest parts of the north-west and midlands and about 1,600 hours on the south-east coast around Rosslare and Arklow. May and June are the sunniest months, with 6 hours a day or more; December manages about an hour and a half. The sky is rarely clear all day and rarely overcast all day, which is why a forecast of "sunny spells and scattered showers" is the most Irish forecast there is. The sunshine tables compare the counties.
Wind
Ireland is one of the windiest countries in Europe at ground level. Malin Head in Donegal has an average wind of about 30 km/h and 66 days a year of gale-force winds; Kilkenny, sheltered in the south-east midlands, averages about 12 km/h. The windiest months are December to February, when Atlantic depressions pass every few days, and the strongest storms come between October and February. The named storms guide covers the big ones.
The seasons
Forecasters count spring as March to May, summer as June to August, autumn as September to November and winter as December to February. Irish tradition starts spring on St Brigid's Day, 1 February, and summer on May Day, which says something about how early the days lengthen here: there are 17 hours of daylight in Dublin at midsummer and about 7½ at midwinter. The seasons page shows how each county's year unfolds.
A warming climate
Ireland's average temperature has risen by close to a degree over the past century, and the warmest years in the record have almost all come since 2000. Wetter winters and more intense downpours are expected to follow. The climate figures on this site are averages for recent years, so they already reflect some of that change.