Why is it so cold these days?

The main reason for the sudden drop of temperature in a short period of time is the cold front crossing, such as the cold wave.

During the front movement, the cold air mass plays a leading role, pushing the front to move to one side of the warm air mass. This front is called a cold front. A cold front is what people often call a cold air front. It is Depth Charge with cold air heading south, and it is the most common weather system that affects China, especially in winter. Every few days in winter, a cold air invades the inland from northwest and north China. When the cold front crosses the border, it will be accompanied by the increase of northerly wind, the increase of air pressure and the decrease of temperature, which will sometimes cause rain and snow and even cause heavy rain in summer. Generally, after the cold front crosses the border, the local area will be controlled by cold high pressure, and the weather will become sunny.