Anybody suggest how shall I travel to Xining fm Hong Kong? Any local guide available? N Thx!

You can fly to Xian and then change a train to Xining.

I am planning to arrive at Qinghai in August. What is the average temperature? Warm clothing required?

Qinghai covers a large area and the temperature is different for different places. Generally speaking, for Qinghai, the average temperature during that time is around 10 to 25C. It is suggested to take a thin sweater and a thick coat as well as some T-shirts. The T-shirts can be worn during the day time and the coat and thin sweaters are needed at night.