Kunming is not hot for the high altitude, but it has strong sunshine. In July and Auguest, the hottest period of a year, the temperature in Kunming will be not more than 31 degrees. It is a bit hot during the day under the sun, quite cool at night. So, you should bring long pants and light jacket apart from summer clothes. Bring sunglasses and hat. Well, bring umbrellas. It is hard to say when it rains, but it will stop very soon. Hope it is ok for you. Have fun!