Humidity significantly influences exercise performance by affecting thermoregulation and hydration levels. High humidity can lead to increased sweat production without effective evaporation, making it harder for the body to cool down. This can result in overheating and fatigue, ultimately impairing performance. Conversely, lower humidity may allow for more efficient cooling, enhancing endurance. Therefore, understanding humidity levels can help athletes prepare adequately and potentially adjust their training regimens for optimal performance in varying environmental conditions.