I assume you are a woman? Will the wedding be in Ireland? Are you from the US or Canada or another country? What's your approximate age? Will you be a guest, a member of the family or in the wedding party?
I am from the U.S. and the wedding is in Ireland this summer. I am a 64-year-old woman. I will be a guest. It is my daughter's sister-in-law. I have never met her. Thank you!
Dress for women at Irish weddings tends to be fancy. If you were 20-something you would probably wear a low-cut "c o c k t a i l " dress. That's why I asked how old you are. Since you are 60-something, probably something a bit more conservative. An elegant suit, a fancy dress or something like that. Of course if you are one of those lucky 64-year-olds that still look like a 20-year-old, then go crazy!
Is a black, long dress appropriate? Will it be cool enough to need a coat or something? What do they usually wear for that? Thank you! I appreciate this.
OK I'm a bloke so a Kilt for a wedding is as close to frock as I am likely to get, but for what its worth. Something smart and tasteful such as a long black dress would be fine. Christina has a Bolero jacket to keep her shoulders warm which is nice, I have seen Shawls worn on fine days and raincoats on rainy days. My answer which infuriates my better half is "Just wear what you feel best in" An Irish wedding is no different to any other and there will be no end of different attires so comfortable class will be absolutely fine. Just get over here, turn up and most of all enjoy yourself.
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Two rules for Ireland, Take your time & bring a sense of humour
The black dress is fine. Although I generally see brighter colors at weddings. As Tony suggested a shawl or jacket. It is hard to predict the weather in Ireland. Also depends on where and when the wedding is. There is usually a lot of dancing at the weddings, so perhaps comfortable shoes. I know - that is an oxymoron for wedding attire!