Moving air removes heat from exposed skin more rapidly than still air. The resulting lower perceived temperature is the wind chill. It matters only when the air temperature is already cold and the wind is blowing.

Wind-chill charts combine air temperature and wind speed into an equivalent temperature that estimates how cold the air feels on bare skin. The index is used to warn of increased risk of frostbite and hypothermia. It does not apply to inanimate objects or to temperatures above freezing.

Modern formulas are based on human physiological responses rather than earlier simple approximations. Weather services publish wind-chill values alongside the actual temperature during cold, windy periods. Outdoor workers and winter sports enthusiasts rely on the information to dress appropriately and limit exposure.

• Perceived temperature due to wind
• Relevant only in cold conditions
• Increases frostbite risk
• Reported with actual temperature