05/11/2026
Japanese researcher Toshiaki Ichinose wanted to find out which clothing colours stay coolest under the hot summer sun. To test this, he carried out an outdoor experiment at Japan’s National Institute for Environmental Studies. The weather was around 30°C, and he placed nine polo shirts of different colours side by side under direct sunlight for five minutes.
Using a thermal camera, he carefully measured how much heat each shirt absorbed. The results showed a big difference between light and dark colours. The white shirt stayed the coolest and remained close to the air temperature at around 30°C. Yellow was the second coolest colour, followed by gray, red, purple, blue, green, dark green, and finally black.
The darker shirts absorbed much more heat. Dark green and black shirts became extremely hot, with temperatures going above 50°C. This showed that dark colours attract and hold more heat from sunlight, while lighter colours reflect more sunlight and stay cooler.
The findings were supported by another large study involving several countries. Researchers discovered that people wearing light-coloured clothes under direct sunlight had skin temperatures that were 12–13% lower than people wearing darker clothes.
The experiment explained why many people prefer wearing white or light-coloured clothing during summer. Light colours can help people feel cooler and more comfortable, especially in hot weather. The study may also help outdoor workers and athletes choose better clothing for staying safe and avoiding overheating during extreme heat.
