Dear Mr Ponch,
Sorry to disappoint you but we are making the trip early May now. By then, weather should be fine. I'm just back from Zhangjiajie, the mountains are scenic & beautiful indeed .... I'm sure you'll enjoy the beautiful mountains & lakes at Zuijaigo & Huanglong too, do make sure you go (if weather permits) since you're at Chengdu already. Have a good trip.