In summer, lightweight, breathable, and quick-drying shirts are important, which quickly wick away sweat and ensure good air circulation. They keep the body cool and dry. Winter requires running shirts made from warmer, insulating material, which also transports moisture away from the body to avoid overheating and cold.
You can find a good overview of trail running in winter in our blog post “Trail running in fall and winter – 10 tips for a safe running adventure”.