To be fair, the heat in Ireland is not really heat at all compared to what they get elsewhere.
If you haven't been abroad in proper heat then there really is no way to explain it to you.
Actually, when you open the oven door and you get a blast of heat in the face, this is what it's like when you walk out of an air conditioned room!!
Don't worry about it anyway. Wear a hat and drink water. You'll get used to it in a day or two.