What is the weather in Sept for Shanghai, Xian,and Beijing? Can I still wear open walking sandals?

In Sept. the average temperature is about 15~26 in Beijing and Shanghai, while it is about 21~27C in Shanghai. It is generally mild in Beijing and Xian and you may also feel hot in a fine day afternoon. It is still a bit hot in Shanghai. It rains much in Xian at that time, while it has proper rain in Beijing and Shanghai. You can wear open walking sandals at that time. Summer cool clothes are OK, better take a piece of jacket or light coat.