time of typhoon that start in Hong Kong?

Typhoon often happens in July, August and September. It's more frequent in August.

Typhoons can start in HK in May and have happened in HK as late as November. The most common time for them is September. That's when Typhoon Wanda devastated many people's lives in the 60s. They usually don't last for more than two days so if you're in Hk for a week you should relax - the wind won't disrupt you're stay too much.