How is hong kong weather for 27-31 july? Then is there any big sales during that time? Any typhoon?

It will be hot and wet. The average temperature should be around 30C. It will rain frequently, both heavy rain and thunderstorm, so umbrella or raicoat would be necessary. It will be during the typhoon season, but it is unpredictable whether it will happen. Therefore, just check the weather ahead.

As I know, there will be many big sales then. So you can go and see!