In July 2018,the weather and climate in the northern hemisphere were significantly abnormal,and extreme events occurred frequently.Much of Europe,North Africa,East Asia and many parts of North America were affected by severe heat waves.Extreme precipitation occurred frequently in southern and northern India,Southeast Asia,southwestern China,and western Japan.The tropical cyclone activity in the western Pacific was extremely active,and the movement path was northerly.The preliminary diagnosis results show that the abnormal high-pressure system maintained from the low to upper level is the direct cause of the heat wave in the middle and high latitudes of the Northern Hemisphere.The enhanced and northward subtropical high and the enhanced and eastward South Asian high are directly related to the persistent high temperatures and extreme precipitation events occurring in East Asia.The extremely active convective around the low-level Philippines and the strong southwest water vapor transport have led to extreme precipitation in South Asia and Southeast Asia.In addition,the warmer sea surface temperature conditions in many parts of the tropical Pacific and the abnormal cyclonic circulation near the Philippines are associated with unusually active typhoon activities.It is important to note that the anomalies of the atmospheric circulation in the Northern Hemisphere,especially in East Asia,are mainly affected by the thermal conditions of the ocean surface and the teleconnection of atmospheric circulation in other regions.Noticeably,the linkage between large scale extreme events in July 2018 and climate change is worthy of further study.