Abstract:Climate characters were analyzed over China in summer 2011. It was found that, the mean temperature was higher than and the precipitation was less than normal in China. High temperature extremes were observed in extensive regions including western Northwest China, southern North China, the Yangtze and Huaihe River Valley, areas to the south of the Yangtze River, eastern Southwest China, and so on during some periods. Severe persistent droughts occurred in the eastern part of Southwest China, but significantly more rainfalls than normal occurred in the Lower Reaches of the Yangtze River. Possible causes for droughts in eastern Southwest China and more precipitation in the Lower Reaches of the Yangtze River were discussed further. Results showed that continuous anomalous high pressure over Southwest China， weak water vapor transports from the Bay of Bengal and the further east location of the western Pacific subtropical high directly caused the Southwest China drought. And the central type La Nina event developing from autumn 2011 may be an important external forcing impacting the drought in Southwest China. The negative phase of AO maintained during summer 2011, and then the polar vortex was weaker than normal, which was advantageous for southward shift of cold airs to affect China. At the same time, the anomalous anti cyclone circulation responding to the negative SSTA in the mid latitude West Pacific intensified the western Pacific subtropical high. And then the northward water vapor transport was stronger than normal. Cold airs met with the moist and warm water vapor and then caused abundant rainfalls in the Lower Reaches of the Yangtze River.