Why is the air pressure lower in rainy days than in sunny days?

The airflow flows from high pressure to low pressure. Under the control of high pressure, high-altitude air flows downward. The sky is not easy to form clouds and rain, so the sky is clear. Under the control of low air pressure, the air flows from the ground to the sky, bringing rich water vapor to the sky, and the water vapor condenses when it meets cold to form clouds and rain.

Or because of high pressure control, the temperature near the ground is low and the air sinks (hence the name high pressure). Of course, the water in the air sinks, because the temperature near the ground is high and the air can hold more water. At this time, there is little water and no clouds in the sky, so it is sunny. On the contrary, the air pressure is low, the temperature near the ground is high, the air rises, and the water also rises. The temperature at high altitude is low, and the water vapor condenses into water droplets, so it can be.