Excuse me: Why is it always hot and stuffy one or two days before the arrival of strong cold air or strong typhoon?

cold air

Explained by the ground temperature field, before the arrival of cold air (cold air mass), this place was controlled by warm air mass. Generally, the temperature and humidity of the heating mass are relatively high, so it will be sultry.

Explain it by monsoon circulation (this explanation can only be used in spring and autumn). Before the cold air comes, it is controlled by warm and humid summer monsoon (southwest monsoon or southeast monsoon) and sultry, and then it is controlled by dry and cold winter monsoon (northeast monsoon or northwest monsoon).

Explained by westerly ridge, cold air is generally due to the passage of high-altitude low-pressure trough; Before the trough of low pressure crosses the border, it is usually controlled by the ridge of high pressure (spring, autumn and winter) or subtropical high (summer). Downward flow prevails under the ridge of high pressure, so it will be sultry.

typhoon

Outside the typhoon's cloud system, there is a downward flow (the reason for the formation of the downward flow is a bit complicated. It doesn't matter if I don't understand it: the reason for the downward flow is that the airflow diverging from the typhoon center moves outward and sinks). The temperature in the subsidence area is high, and sometimes the temperature above 38 degrees can be off the charts.