Before you come to Dublin, make sure to read this article about the climate in Ireland and the weather in Dublin carefully. It is important to be well prepared for this before arrival, because if not you might get very surprised and also a bit sad.
Ireland is a green island, and to stay green it needs lots of rain. And lots of rain you will experience while in Dublin and in Ireland. In general it can be said that the climate of Ireland is moist, it changes quick, but it is seldom very extreme. This means that in the summer it does not get to hot, and during winter time it is not to cold. It rains very often, so even though the sun shines as you leave your Dublin hotel, it might rain 5 minutes later, without any warning. But, just as quick as the rain appeared, it will disappear again. If the rain comes, just stop in a pub and drink a Guinness, and afterwards, walk on again!
The climate varies between the east and the west, but the number of wet days (days with more than 1 mm of rain) ranges between 150 and 225 days a year.
If you visit Dublin you will probably not meet any snow. At some places in Ireland it might snow up to 30 days a year, but at the lower places they are lucky to see the snow a couple of days a year.
If you wonder what the weather is like in Dublin right now, see the weather forecast further down!