I intend to visit Chengdu in mid May and to Jiuzhagou, Leshan and Mt Emei, can I check what is the temperature then?

I am afraid that it is so early to know the temperature in May this year, but I can tell a general situation for that time according to the previous records.
For CD, the average tempreture is around 18 to 25C and the similar situation for Leshan. For Emeishan City, the average temperature is around 6 to 13C and you need to prepare thick coat since you want to climb the mountain. For Jiuzhaigou, it is around 10 to 20C. The weather in that valley is changeable and it is suggested to prepare rain gear in case of the rain.

in mid May it won't be too cold. an average temps will be around 20 degree