Hi Julie,
This tour currently has 29 travellers booked, with 20 taking the main tour only and 9 taking the Hong-Kong add-on.
Weather is so unpredictable now-a-days it is always worth checking just before you go, but historically May is the end of the Spring season - temperatures have highs in the early 20s and lows around 14 degrees. It is possible for some rain, so make sure you pack a waterproof coat and possibly an umbrella too.
Kindest regards,
Julia