It's a local saying that Dublin doesn't have a climate, it has a weather. In Dublin you get all Four Seasons of the year crammed into each day. Early mornings are usually fine. Late morning to lunch time is the likeliest time for a good Autumnal rain shower. By the middle of the afternoon you think it is Summer and in the evening you're back to Winter. Exceptions to the rule do exist, but you can always rely on the fact that no weather condition - good or bad - is going to last for long. Remember this as a comforting thought the next time you get caught in a rain shower.
Thanks to its location by the Irish Sea on one side and flat open hinterland to the North and the West, rain clouds are dispelled fast by the coastal winds. These winds are very reliable throughout the year and Dublin boasts a sizeable sailing and kite surfing scene as a result. On a calm day during the Summer you often get sea mist pouring into the lower parts of the city while the sun shines on higher ground.
Mild Winters, Tepid Summers
For most parts of the year, temperatures in Dublin range from 5°C to 18°C. The low fluctuation in temperature makes Dublin an ideal year-round destination for weekend breaks and sightseeing.
Dubliners are used to the modest Summer temperatures and make the most of every sun ray. Many cafes and restaurants, particularly in the city centre, spill out onto the sidewalk offering al fresco dining during the Summer months. If the thermometer hits 20°C the whole city develops a noticeably cheerful carnival atmosphere.
Summer temperatures in Dublin might be modest, but in return you also get very mild Winters. It is not unusual for temperatures in the run-up to Christmas to reach a balmy 8°C.
Dublin has a reputation for being a rainy city, but the statistics would suggest otherwise. Dublin has on average 11 rainy days and 70mm of rain per month. That's less than, say, Brussels (Belgium) and not significantly more than Frankfurt (Germany). If it does rain in Dublin, chances are it will not last for long. Do what the locals do, duck into a cafe or pub and wait for the shower to pass.
Dublin weather forecast