Why does the air in the center of the low pressure area flow from bottom to top, and why does the air flowing from bottom to top mean rainy weather?

The air in the center of the low-pressure area is squeezed by the surrounding air, that is, the pressure difference is generated, so that the air near the center keeps approaching the low-pressure center to form an airflow, and the air in the lower part of the low-pressure center will be forced to move upward. For example, it's like squeezing toothpaste and pinching the toothpaste skin, which makes the pressure difference between the center and the surrounding area, and the toothpaste comes out from above. As for why there is rainy weather, it is a geographical problem. Generally speaking, the water content in low-altitude air is relatively lower than that in high altitude (gravity), and the updraft brings water vapor to high altitude, and the temperature in high altitude is relatively low, which makes water vapor condense and prone to rainy weather. But there will be special circumstances, that is, when the surface is very, very dry, such as in the desert, it may not be rainy. Well, if the landlord is not clear, please ask. I'm also interested in geography, Di ~ ~ ~