Why is the air pressure greater on sunny days than on rainy days? The atmospheric pressure in winter is greater than that in summer?

In rainy days, the air contains a lot of water vapor, which is a factor affecting atmospheric pressure. Atmospheric pressure is produced by the movement of air molecules, so the atmospheric pressure of air containing water vapor becomes smaller.

In winter, when the temperature is low, the density of air is relatively high. But air pressure is related to density. The higher the density, the greater the pressure. So the air pressure in winter is higher in summer. Of course, there are many factors that affect air pressure, and these are just one aspect, such as airflow, humidity, season, typhoon, weather and so on.