Why is the high-pressure area sunny and the low-pressure area rainy?

High pressure is formed by air sinking, and low pressure is formed by air rising.

High air pressure: air sinking makes fine particles such as dust in the atmosphere sink. Relatively speaking, there are fewer particles in the atmospheric space. As we all know, one of the necessary conditions for the formation of rainfall is to have condensation nuclei. In addition, because the air sinks and the temperature rises, water droplets evaporate into steam, making it difficult to form rainfall conditions. Therefore, it is difficult for the atmosphere with less particles to rain in the clouds, that is, the weather is fine.

Low pressure: Rising air drives fine particles such as ground solid dust to rise. During the rising process, the air temperature drops, water vapor condenses into water droplets, and fine particles act as condensation nuclei, resulting in cloud-like rainfall. This is why the air pressure is low and it is rainy.