Why is the weather always bad around the thirteenth day of the first month?

1. Cold air affects North China and its south.

From March 3rd to 4th, cold air affected North China and its south area. There are northerly winds of 4 ~ 6 in most of the above areas, and the temperature drops by 4 ~ 8℃, and the local temperature drop can reach 10℃. In addition, there was light snow or sleet in parts of Jianghuai, Jianghan and northern Jiangnan from 4th to 5th.

There is moderate to heavy snow in southern Tibet.

On the 3rd, there were small to medium snows in southern Tibet, southern Qinghai and northern Sichuan Plateau, among which there were moderate to heavy snows in parts of southern Tibet.