During my research for this question, I happily stumbled upon some other quite interesting information about raincoats in China, especially amoung the royals.
Wealthy families wore 'Jade Needle' capes that were made from a high-class grass that was waterproof and extremely soft.
Royal coats were made from pipal tree leaves after they were woven together, which gave the coats the name 'Papal' coats. Despite the fact that is was called a raincoat, it was actually a rain suit. it was comprised of a coat and a straw apron.
The Qing dynasty's emperors and officials wore designated colour coats. Yellow coats were worn strictly by the emperor, while red coats were desiganted for princes and high court officals and cyan coloured coats were made for second ranking officials. During the winter season rain coats were made from felt to help insulate body heat.