Today, when it gets warm, we think we need to remove clothing, because it is socially acceptable to do so. This way, we don't need to be as inconvenienced by the seasons. Unlike the extremely seasonal lives of our ancestors, our lives run year-long, not offering any variation based on the season. We are spoiled by air conditioning and heating systems as well as our recreational activities.
We assume that the only way to cool down is to remove clothing (or wear less of them)- that it is the inherent properties in clothing that are making us overly warm. This isn't always the case though. Think about it, have you ever sat in a car wearing something black? I have, I was wearing a new black skirt and the sun was shining right on my lap and I was frying. My mother offered me her white sweater and I refused saying it would just make me hotter. However, eventually I gave in and you know what? It made me cooler! Adding a white layer actually reflected the sun enough that I could feel a difference. There is a reason that you see women's clothing from older time periods in white. We rarely wear white these days, even pastels aren't really "in fashion" but for summer clothes, white is essential. Now, I am a plus sized woman and the thought of draping myself in white is not appealing, so for now, I try to stick to cotton because it breathes, and as light a color as I dare to go, especially on top. It really does help!
AND DRINK LOTS OF WATER!!! Sweat is your body's own air conditioning, if you are not hydrated, it doesn't work. Common sense applies even if you are wearing tank tops and cut-offs or a beautiful flowing dress- stay out of the sun and keep covered when you are in the sun!!!