The main characteristics of the atmospheric circulation in the autumn (from September to November) of 2020 are as follows. The polar vortex is characterized by a single-pole type in the Northern Hemisphere and the circulations present a 4-wave mode in middle and high latitudes. From September to November, the meridional gradient of the Eurasian mid-high latitude circulation is increasing and the cold air is strengthening. The western Pacific subtropical high is stronger than the historical average and tropical cyclones are frequent. There were 19 gale processes above 8 grade over offshore areas of China, including 6 produced by cold air, 4 by typhoons, one by extratropical cyclones, 7 jointly by cold air and tropical cyclones, and one jointly by cold air and extratropical cyclones. There were 13 tropical cyclones generated over western North Pacific and the South China Sea, among which 7 typhoons were generated in October, equalizing the highest number of typhoons in October. In addition, 26 tropical cyclones were generated over the world's other oceans. There are only 12 days without rough sea wave processes above 2 m over offshore areas of China, accounting for about 13％ of the total days of autumn. In autumn 2020, the sea surface temperature (SST) has an overall trend of decrease, while the decrease rate in northern seas is obviously larger than that in southern seas. Due to the continuous activities of tropical cyclones that move northward affecting the northern waters of China, the SST over the eastern Yellow Sea and the eastern East China Sea in September is significantly lower than the climatology.