Why do my feet get colder in thick socks than thin ones?

Thick socks in properly fitted ski boots compress your foot, restricting blood flow to your toes. Reduced circulation means colder feet, regardless of how much insulation the sock provides. Additionally, thick socks retain more sweat, and damp skin loses heat dramatically faster than dry skin. Lightweight socks avoid both problems by allowing natural circulation and wicking moisture efficiently. This is the most common revelation for skiers who switch to lightweight socks.