What is necessary for the effective evaporation of sweat for cooling the body?

For the effective evaporation of sweat, low humidity is essential because it allows the moisture from sweat to transition from liquid to vapor more efficiently. When humidity levels are high, the air is already saturated with moisture, making it difficult for additional moisture—such as sweat—to evaporate. This process of evaporation absorbs heat from the body, which is how sweating cools us down. In contrast, high humidity reduces the gradient between the skin's moisture and the surrounding air, thus hindering the cooling effect of sweat evaporation. Therefore, low humidity creates optimal conditions for sweating to effectively lower body temperature.