Why is the pressure low on cloudy days?

The reason why cloudy weather is low is because oxygen concentration is low and atmospheric pressure is low. Winter is dry and cold, the air density is greater than in summer, and the water vapor content is less than in summer, so the oxygen concentration is higher than in summer. The water vapor content in the air on a sunny day is much less than that on a cloudy day, and the relative oxygen concentration is higher.

When winter is cold, the distance between air molecules is small and the density is high; on cloudy days, when there is more water vapor, the relative density of air is smaller. However, the comparison of air pressure between winter and summer, sunny days and cloudy days is usually based on human feelings, not academic. People's feelings about the level of air pressure are determined by the oxygen concentration, so it is more appropriate to discuss the level of oxygen concentration here.