We want to go to Jiuzhaigou in the middle of May. What will the temperature be on those days ?

The scenery is beautiful and the price is cheaper than that in October. The temperature difference is big, so it is suggested to take your coat and a thin sweater in case of the rainy days. The temperature is around 15 to 20C according to the previous records.
The oxygen is not necessary in JZG, but if you want, you can buy or rent a oxygen bag there.