Abstract:The main characteristics of the general atmospheric circulation in May 2020 is that the circulation finished the transition from a three wave pattern to a four wave pattern in middle high latitudes of the Northern Hemisphere, and the South China Sea summer monsoon erupted in the fourth pentad. In addition, there was one polar vortex center in the Northern Hemisphere, slightly weaker than usual. The strength of Western Pacific subtropical high was a little stronger than that in normal years, and the south branch though was a little weaker. The monthly mean temperature was 17.2℃, 1.0℃ higher than normal, which ranks the fourth highest since 1961. The monthly mean precipitation amount was 68.5 mm, closed to normal (69.5 mm). Six regional torrential rain processes occurred in China this month. The earliest high temperature process since 1961 occurred in the central and eastern China in May, and the highest temperature in many places exceeded the historical extreme values of the month. Severe droughts occurred in Jianghuai, Huanghuai and Yunnan, and two sand dust weather events happened in the northern part of China.