The following are the main characteristics of the general atmospheric circulation in December 2012. There is one polar vortex center in the Northern Hemisphere, and the circulation presents meridional patterns in middle high latitudes, which is in favor of leading cold air southward. The south branch trough behaves actively and the subtropical high is stronger than normal years’. The monthly mean precipitation over China is 17.6 mm, 67.6% more than the corresponding month of normal years (10.5 mm). The monthly mean temperature is -4.4℃, 1.2℃ lower than the normal temperature at the same period, of which the mean temperature of Beijing breaks the lowest record in history (-3.2℃). There are five obvious cold air processes and four rainfall processes in the month. Many regions experience extreme cold and extreme day temperature dropping events, and part of northern China suffers snow disasters. Besides, large scale persisting rainy weather appears Jiangnan, South China and other places in southern China.