Abstract:In January 2026, the main characteristics of the atmospheric circulation in the Northern Hemisphere are that the polar vortex was distributed in a dipole pattern, and the center of polar vortex in the Eastern Hemisphere was located in the Central Siberian Plateau, which was weaker than that in the same period of normal years. The circulation in the middle and high latitudes of Eurasia presented a “two troughs and one ridge” distribution. The East Asian trough was stronger than usual, and the cold air path affecting China was by east. The Northwest Pacific subtropical high (WPSH) was slightly weaker than normal, while the southern branch trough was weaker than normal. Under such circulation background, the national average precipitation in January (6.3 mm) was 56% less than that in the same period of normal years (14.3 mm), with an uneven spatial distribution, i.e., more in the north and less in the south. The national average temperature was -4.0℃, which is 0.8℃ higher than normal (-4.8℃). During this month, five cold air activities occurred, of which there was a cold wave weather process during 17-21 when the temperatures in the central and eastern regions of China dropped sharply. The minimum temperatures at six national stations broke through the historical extreme values, accompanied by a wide range of rain and snow weather, and the phase transition of precipitation was complex. Freezing rain or ice particles appeared in Guizhou, Hunan and Hubei, posing a serious impact on road traffic and power. In addition, there were three sand dust weather processes and three fog haze weather processes in the month.