Wear black clothes in the summer?

That counterintuitive recommendation comes from The Straight Dope, via io9:

We're all encouraged to wear white in summer, since white clothing is supposed to keep us cool — but it doesn't. In fact, black clothing is the best way to keep cool in the heat. It's basic physics. And biology...

This means that white clothing reflects a great deal of wavelengths of energy coming in. This means it should reflect the sun's rays back, instead of letting them cook us. And that's perfectly correct.

Except that this explanation is also incomplete. Heat is not just coming in off of the sun. It's also coming off a person's own, sweating, warm-blooded, mammalian body, which is a lot closer than the sun is. When all that body heat hits the white clothing covering it, it gets reflected right back towards the body. When we wear white, we cook ourselves.

The best color to keep cool in the heat, it turns out, is to wear black. Black absorbs everything coming in from the sun, sure. But black also absorbs energy from the body instead of reflecting it back.

I think this is oversimplified and perhaps misleading, but there is additional discussion re wind and atmospheric conditions at the link, though apparently no discussion of hot sunny days vs hot cloudy days.