A fan in summer will speed up the air flow, although it can't lower the temperature, but by speeding up the air flow, the sweat of the human body will evaporate quickly. Evaporation is the process of absorbing heat. When sweat evaporates, it will absorb some heat from the human body, so we will feel cool.
The temperature in summer is very hot, so we should take some measures to prevent heatstroke. Don't be exposed to the sun for a long time, and don't do strenuous exercise. We can eat some cold fruits and food to relieve the hot feeling.