Is it cold to travel to Tengchong in September? How's the weather?

It's not cold, you can take a cotton coat, but you don't need a down jacket. You can refer to autumn clothes, and there is less rain after winter. Tengchong is cold, Ruili and mangshi can still wear short sleeves at noon, but the temperature difference between noon and morning and evening is about 10 degrees. Keep warm in the morning and evening. Cold, wet and cold, very suitable for hot springs. Pay attention to sun protection, ultraviolet rays are a little strong.