Hi I intend to go to Hong Kong Disney from 20th August onwards. How is the weather?

I just checked the weather records of the past several years. It showed that it is hot on that day, with the average temp of around 28C (82F). It may be cloudy or rainy. I suggest you prepare summer clothing and light raincoat. Also it is necessary to check the weather forecast beforehand, because it is during the typhoon season.