One of the things that you can expect when you go to Ireland is the weather is going to be very erratic. One moment it would be raining, then the next time, the sun will come out, and you would feel a bit warm. Women in Ireland wear simple shirts as undergarments in order to protect themselves from the cold. They wear it under open sleeved dresses.
You can also expect that they will be wearing a kilt. One of the greatest misconceptions of people is that only men in Ireland wear the kilt, but actually, the women also wear the kilt because this is their sign that they are free. There was even a time when most of them wore mostly yellow as a sign of rebellion from England. Things have changed greatly now, but they still remember their traditional clothes.