Zhangye Rainbow Mountains in March

May through October gives you the best weather and longest daylight hours. July and August are peak season - expect crowds but also the most dramatic lighting. September is the sweet spot - fewer tourists, stable weather, and those crisp autumn mornings that make the colors pop. Winter visits are possible but temperatures can hit -20°C, and some platforms may be icy. For photographers, the hour before sunset is magic - the low angle light brings out every stripe and layer. Sunrise is gorgeous too but requires staying overnight in Zhangye city since the first shuttle doesn't run early enough for dawn shots.