Why is the fan on sometimes when the weather is not hot?

That's because our skin has sweat glands, and the air humidity is too high to dissipate the heat on the body surface, so we have to use a fan to let the air flow and evaporate the sweat on the body surface, which will take away the heat, so we can't feel the heat. When we go back to the southern sky, the temperature is not high, but we will feel sultry. In fact, it is because the air humidity is too high and the air is not circulating, so we will feel hot and turn on the fan.