Part of the reason I asked the question is that I have a base-layer garment that I bought probably 20 years ago. I bought it to help me, I thought to stay warm. When I wore it, in 55-60 degree weather I found that I froze myself. I had thought that it was was for cold weather since it had a long sleeves. Obviously, I discovered that this was intended for warm weather. I hardly wore it since. But after all this conversation I wore it this week on a day when the temperature was 80 and the humidity was very high. Must admit, that it kept me cooler. There is the bulkiness of an extra piece of clothing. But I was surprised that overall it felt cooler.