The main characteristics of the atmospheric circulation in the winter of 2017 (from December 2017 to February 2018) are as follows. The polar vortex was characterized by the dipole type in the Northern Hemisphere and 4-wave mode in middle and high latitudes. In December, the atmospheric circulation was in meridional pattern in middle and high latitudes of central and eastern Asia, which was favorable for the southward of the cold air. In January 2018, the cold Siberian High was stronger than that in December, and cold air affected offshore areas from north to south. In February, cold air was weaker, and extratropical cyclones appeared over seas and developed. There were 19 gales over 8 grade in offshore areas, including 14 gales produced by cold air, 2 by cold air and extratropical cyclones, 1 by cold air and tropical cyclones, and 2 by tropical cyclones. There were 19 rough sea wave processes above 2 m and only ten days were without wave processes above 2 m. Six obvious sea fog processes occurred over offshore areas, mainly near Beibu Gulf from night to morning. Four typhoons occurred over western North Pacific and the South China Sea. The sea surface temperature showed downtrend on the whole.