Take a light, oversized raincoat. This should be large enough for you to be able to easily throw it on over any other clothes you may be wearing to keep them as dry as possible.
Pack clothes of different types of fabrics and thickness, which will allow you to wear several layers. Irish winters can be brutally cold, and many Irish people keep their homes very warm inside, especially during winter. If you wear layers, you will be able to easily make the transition from cold to warm and back to cold without needing to change your entire outfit.
Avoid taking too many clothing items that require special care. You will probably find that all your clothes begin to feel damp after a while, and you may wish to simply throw them into a clothes dryer for a few minutes to dry them out and warm them up before getting dressed.
Take a pair of rubber boots if you plan to spend a lot of time outside, especially if you will be in the countryside rather than in one of the main cities. Much of the Irish countryside becomes very muddy during the winter, and you can easily ruin your shoes if you hike around in them.
Include at least one scarf and one hat that covers your ears in your luggage. Having a brisk wind blow sharp droplets of Irish rain down your shirt collar and into your ears is not the most pleasant way to spend your vacation.
Pack a pair of warm, water-resistant gloves if your hands are susceptible to the cold or if you plan to spend much time outside.
Stuff a few empty garbage bags into your suitcase before you leave. You may find that you have a pair of muddy boots, a dripping raincoat and several soaked sweaters when you are packing to head back home. You can put these into garbage bags and tie the tops to protect the rest of your belongings until you get home and have time to wash and dry the wet or dirty items.
