The main characteristics of the general atmospheric circulation in October 2017 are as follows. The polar vortex showed a dipole pattern. The circulation presented a fourwave pattern in middlehigh latitudes. The northwestern Pacific subtropical high was stronger and remarkably more westward extended than normal. The monthly mean precipitation amount was 46.2 mm, which is 29% more than normal (35.8 mm), ranking the top 8th since 1961. The monthly mean temperature was 10.6℃, 0.3℃ higher than normal. There were six largerange heavy rainfall processes and three cold air processes over China, of which the rainfall process from 8 to 10 October was accompanied by cold airs, resulting a rarelyseen largerange heavy rainfall in Autumn over North China. On 16 October, Typhoon Khanun (1720) made landfall at Leizhou Peninsula, Guangdong, bringing gale and rainfall to South China. In late October northern China suffered a foghaze event.