How is the sultry weather formed?

There is always a sultry period before it rains, and there is little cool wind. This is because:

1. Summer rainfall is generally caused by the combined influence of cold air and warm and humid airflow, while sultry is the expression of the increase of water vapor and temperature in the atmosphere. This is also a precursor to summer thunderstorms.

2. Most of the rain in summer is showers and thunderstorms, which is due to the fine weather, high temperature and strong air convection in some areas, which makes a large number of hot and humid air rise sharply and form cumulonimbus clouds. At the same time, the hot air in the atmosphere is increasing and the water vapor is sufficient. Although the temperature has not changed much at this time, the water on the ground is not easy to evaporate, and the sweat on people is not easy to volatilize, so it will feel very stuffy and uncomfortable.