When is the best weather for traveling to Lhasa and Beijing. What are the weather conditions in each city. what type of clothing is needed.

Well, July to August is suitable to travel in Lhasa. During that time, the lowest temp is about 9C and the highest temp is about 26C. Due to the big temperature gap between daytime and night, you'd better take thick coat or jacket to keep warm in outdoor at nights.

As for BJ, the best travel season should be around Sep. and Oct. It is also the high travel season there. During that time, it is fine in most cases, with the average temperature of around 22C. And it may rain a little sometimes. If you wanna travel then, long-sleeved, light coat and jeans are necessary.