Before the summer rainstorm, the weather is sultry and dark clouds are rolling. Try to analyze and explain why this phenomenon occurs.

It's the air pressure. After the air pressure that the human body adapts to suddenly becomes lower, the pressure in the body will be greater than the external pressure ~ The heat and moisture in the body will be lost in large quantities ~ It will be dissipated from the body surface in the form of radiant heat and sweat ~ So it's sultry

The dark clouds are rolling because the clouds are mixed with each other ~ Because of the different densities, the light will be reflected or refracted ~ So it's a black cloud ~