You've got to feel good in the summer heat in order to look good. Extreme heat can be hazardous to your health as well as your public persona. Besides remaining in air-conditioned settings and drinking plenty of fluids to help the body regulate heat, the Centers for Disease Control and Prevention recommends wearing loose, lightweight, light-colored clothing.
A 2011 Mayo Clinic report regarding heat stroke states with no uncertainty that wearing light-colored clothing is key to regulating body temperature during the summer months when sun exposure is at its highest. Whereas dark-colored clothing absorbs heat from the sun, light-colored clothing reflects the sun's heat away from the body to help it stay cooler.
When attached to thermometers and exposed to sunlight, strips of black paper or cloth have been found to heat to higher temperatures and faster than white materials in comparative tests. Experiments have shown that dark shades of green, blue and purple actually generated thermal energy when exposed to intense sunlight, while lighter colors generated less thermal energy under the same sunlight conditions. This experiment can be carried over to apply to clothing in corresponding colors, and how they will react in the sun.
Light reacts to colors in different ways, depending on how much it's absorbed or reflected. Since black naturally absorbs more light that it reflects, more consequent heat is retained. Light reflects more off of white than is absorbed, so white retains less heat.
Since people associate the summer time with sunshine and heat, light-colored clothing may enhance moods in keeping with the season. Perhaps it's a case of the tail wagging the dog, but fashion designers traditionally produce summer season collections in shades of white, beige, pink, and yellow, and people seeking to appear fashionable follow those trends. Clothing made of loosely woven silk, cotton and linen are designers' summer staples because they help keep their customers comfortable and free of the most obvious signs of heat distress: odor and perspiration.