What clothes should I wear to go to Gannan in western Sichuan in late May?

Gannan is the Qinghai-Tibet Plateau, and its climate is wet and cold. Even in May, the temperature difference between morning and evening is still relatively large (except Diebu and Zhouqu County No.7 is better). In other places, you must wear a coat and trousers sooner or later. In case of rainy weather, the temperature is generally14,5 degrees. Due to the strong ultraviolet rays, locals generally don't wear short sleeves.