Men's clothing when it is above twenty five degrees

Short answer: Loose fit beats tight fit. Air between fabric and skin is what actually cools. Color matters less than most people think.

Air between fabric and skin cools

A loose garment lets air move freely and carry heat away from the skin throughout the day. A tight one does not do the same, no matter how thin the material is, since there is no room for the air. See bamboo t-shirts for men.

An undershirt is not unnecessary

A thin layer moves sweat away from the skin and keeps the shirt dry, even on the hottest days. It might seem pointless in the heat, but it actually makes the difference between a dry shirt and a soaked one. See bamboo underwear for men.

Socks in warm shoes

Feet sweat more than almost any other part of the body, especially inside closed shoes during high summer temperatures. Thin socks in a breathable material help more than no socks at all, since they actually carry moisture away. See bamboo socks for men.

Color matters less than fit

Light colors reflect slightly more sunlight than dark ones, but the air space between fabric and skin matters far more for how hot you feel. A dark t-shirt in a loose fit often beats a light one in a tight cut. See bamboo clothing for men.

The weight of the material

A light fabric feels cooler than a heavy one, even at the same temperature and the same cut of garment. Weight decides how much heat gets held close to the body, while a light material lets heat escape faster.

Sleeve length and airflow

Short sleeves let in the most air, but a loose fitting long sleeved shirt can actually shield against direct sun without getting too warm. It comes down to finding the balance between coverage and airflow depending on how much sun there is.

Pants that do not stick

Loose pants in a light material stop the fabric from sticking to the legs when sweating over the course of the day. Tight jeans in thick denim are often the worst choice at high temperatures, no matter how good they otherwise look.

Activity level changes the need

During desk work indoors, fit matters less, since the body is not generating much heat on its own. During physical activity outdoors, the need for airflow and moisture transport rises sharply, and clothing choice should follow that need.

Shade over fabric

No fabric can fully replace shade, but a loose and light garment makes waiting in the sun more bearable in the meantime. The combination of the right fit and actual shade is what makes heat most manageable overall.