Loose beats less. The instinct in real heat is to wear as little as possible, but bare skin in direct sun heats you up and burns. What actually cools is airflow: loose, light fabric that shades the skin and lets moving air do its work — the logic every hot-climate tradition of dress arrived at. A relaxed linen shirt worn open over a tee can genuinely be cooler than the tee alone once the sun is high.
Linen stops being a luxury and becomes the answer. Nothing else breathes like it, it dries fast, and its rumple reads as intentional in a way sweat-marked cotton never does. A linen shirt and linen or airy cotton trousers or shorts will carry almost every 27°C occasion. Second place goes to seersucker and open-weave cotton; last place, emphatically, to anything synthetic against the skin.
Sun protection is part of the outfit now. A breathable cap or a brimmed hat, proper sunglasses, and long sleeves you can roll — from 25°C these do more for comfort than any fabric choice. Light colours reflect heat; there's a reason nobody meets an August afternoon in black. If you burn easily, a loose long-sleeve linen shirt is better protection than sunscreen on a bare arm, and cooler than it sounds.
Feet want air or nothing much. Leather sandals, espadrilles, canvas trainers with low-cut socks — anything enclosed and padded turns swampy fast. This is also sock weather in the technical sense: thin cotton or linen blends, changed daily, because footwear absorbs more of summer than any other category and smells like it if you let it.
Plan around the peak. At 28°C the day has a shape: mornings and evenings are pleasant, two-to-four is punishing. Do the walking early, keep the midday stretch shaded or indoors, and keep one collared, presentable layer in reserve for air-conditioned interiors — the restaurant at 21°C feels arctic after the street at 29°C. Rinse or wash light pieces often; sweat and sunscreen are what age summer clothes, not wear.