Why is it always raining in Wenzhou now?

This question should first explain what frontal weather is.

Usually, the cold air (or warm air) concentrated in a large area is called cold air mass (or warm air mass).

The cold and warm air mass is not static, but constantly moving. When the cold air mass is strong and actively moves towards the warm air mass, we call it a "cold front". When the warm air mass is strong and actively moves towards the cold air mass, we call it a "warm front". The place where cold and warm air masses touch each other is called the front. When the cold and warm fronts meet, because the water vapor in the warm air mass is induced by the cold air mass, the temperature drops and the water vapor liquefies, thus forming precipitation. The warm front precipitation is generally behind the front, and the cold front precipitation is generally before the front. Under normal circumstances, strong air masses will push weak air masses to move, so we often hear the saying that cold (warm) fronts cross the border in weather forecasts.

June is the rainy season in the middle and lower reaches of the Yangtze River. In this season, the southwest monsoon blows from the Pacific Ocean, and the warm air mass carrying a lot of water vapor moves to the land, while the cold air mass moves from the northwest inland to the ocean. At this time, cold air mass and warm air mass meet in the middle and lower reaches of the Yangtze River in China. But this is because the forces of the two air masses are almost equal, and no one can push anyone, so the front system stays somewhere. This front phenomenon is called "quasi-static stop front". The front of the quasi-static front is constantly in contact with cold and warm air, which produces a lot of precipitation, and the middle and lower reaches of the Yangtze River are the places where the quasi-static front stays this season, so there is a lot of precipitation. It is also called "Plum Rain Season" because this season is officially the season when plums are ripe.