Weather in Suzhou, Guilin & Xian in June and September

Hi,

My wife and I are looking at a tour starting in Beijing, going on to Xian, Guilin, Suzhou and Shanghai. The options are either starting 1st June 2014 or starting 31st August 2014. Can you please advise on the likely weather for these two periods and what type of clothing we should pack? I realise that this is a long time ahead, but presume that weather patterns in this area are fairly stable and predictable?

Thanks and regards

Richard Sims