The temperature would be around 35 at day time. Generally, there is a lot of rainfal in June and July, but it won't last long time.

The temperature range on average during that time is 25.9 to 30.3 celcius. It's the most comfortable of the summer months but it's also the dullest of this season and sees the most hours of rain (but still it only rains on average only 12% of the time and mostly in the morning hours). Keep in mind that HK doesn't usually feel like 26-30 celcius in HK during that time but feels more like 33-39. Also, if you plan to go to Victoria Peak, make sure you do go in the afternoon or even in the other months of summer as the rain could disrupt your trip a bit. Cloudier days are more comfortable though but the payoff is that you don't get see how beautiful HK can be under the sunshine. You're not as likely to see typhoons during this month as you are in the latter months but nonetheless they can't be ruled out. Good trip.