Pack a raincoat, poncho, umbrella or all of the above. Ireland is an island and rain is common, so go prepared to get wet.
Select warm clothing such as sweaters, long-sleeved shirts and sweatshirts. Or, wait until you get there and buy one of the wool sweaters for which Ireland is famous.
Include some short-sleeved shirts during the summer months, but plan on wearing long sleeves much of the time.
Pick dark-colored clothing, especially pants. Darker colors hide when you get wet and muddy from the regular downpours.
Bring a windbreaker or a coat. The weight will depend on the part of the year in which you are visiting. During summer months, a lightweight windbreaker over a long-sleeved t-shirt should be enough.
Have a hat at the ready for protecting your head from the chill of coastal winds. Ireland is well-known for its hats, so you could also wait and get one upon arrival.
Choose comfortable, weather-proof shoes for you hiking along the craggy coastal rocks.
Take long johns to wear under clothing, especially if you are going during the colder months.