Climatology characteristics of several hazardous aviation weather phenomena including low visibility and sea fog, low cloud and cumulonimbus, high wind and thunderstorm in China offing seas are analyzed using the ICOADS individual observations，monthly summaries and gridded LISOTD climatological data. Low visibility and sea fogs occur most frequently on the Yellow Sea and the northern East China Sea from May to July. The occurrence frequency of sea fogs in the Bohai Sea Bay is lower except in July. Sea fogs occur less frequently in the southern East China Sea and South China Sea, except for in the coastal regions from January to May. Low cloud occurs most frequently in the East China Sea from November to next April. Especially in January the frequency of sea fogs is so high, and the extent is so extensive as to extend to the southern Yellow Sea and the northeastern South China Sea. The frequent appearance region of cumulonimbus locates in the western Pacific warm pool. The occurrence frequency of cumulonimbus in China costal region is lower. High wind occurs frequently in the East China Sea and northeastern South China Sea, especially in the Taiwan Strait and Bashi Channel, during October to next March. Thunderstorms occur frequently in the coastal regions including the northwestern coastal region of the Bohai Sea, the coastal regions of the Yellow Sea, south of Shandong, and north of Jiangsu Provinces, and the northern coastal region of the South China Sea.