What should I wear to Qinghai Lake in mid-September?

It was already very cold in mid-September. Generally, Qinghai Lake will be closed in the middle and late period of 10. The last time I went was at the end of August, I wore pants, short-sleeved shirts and a cloak. Later, when the sun was shining, I wore a short-sleeved cloak, but people who came back from there two days before we went told us that they were wearing down jackets ... so it depends on whether it is sunny or cloudy. I usually go to this place with thin clothes, T-shirts, thin sweaters and shirts. I can add it layer by layer, and I can take it off at any time in hot weather, and then I can bring a thick coat, such as sweater coat, jacket and thin down jacket.