Wind chill describes how cold the air feels on exposed skin when wind is blowing. Wind removes heat from the body faster than still air, making cold weather feel colder.
Wind chill is not the actual air temperature
The thermometer may show one temperature, but the wind chill can feel lower. It is a comfort and safety measure, not a separate physical temperature of the air.
Why wind chill matters
Low wind chill can increase the risk of frostbite or cold stress because exposed skin loses heat quickly.
Wind chill is the cold-weather cousin of the heat index, which describes how hot air feels with humidity.