Why does the weather suddenly get hot a few days before the cold air goes south in winter?

The temperature rise before the arrival of cold air is related to the development of weather system.

Because China is located in the westerly belt, the southwest airflow is often in front of the trough and the cold air from the northwest is behind the trough. The interaction between the two causes the warm and humid airflow in the southwest to affect the local area before the cold air goes south, leading to an increase in temperature.

Under normal circumstances, this warming phenomenon will last for one day. So in winter, if one day it suddenly warms up, it often indicates the arrival of cold air. This warming phenomenon also occurred before cold air invaded central and eastern China.

Extended data

In the weather forecast about cold air, we will hear the forecast about the cooling range, such as "the temperature in the central and eastern regions will drop by 6℃ to 8℃, and the local cooling range can reach 10℃ to 14℃."

After the cold air really arrives, some people will find that the cooling is not as strong as expected. This is because the cooling range is determined according to the temperature before the arrival of cold air and the temperature after the influence of cold air. For example, if a person advances 3 steps and retreats 5 steps, he actually only retreats 2 steps, but his "retreat range" is 5 steps.