What is the climate and heat like during end of July-August in Hainan?

I'm basically thinking of going for a hoilday in Hainan during the end of July-August this year. However I have heard from my family living there that it is very extremely hot, and most likely to be unbearable. Because I am from the UK, the temperature there doesn't get more that 25 degrees during summer. I feel that I would find it hard to bear during this time peroid, and possibly get sunstroke or heat exhaustion.
Along with wanting to know how hot it can possibly get. I would also like some advice on how to cope with the heat if you were in my shoes, if I were to go.
Would be great if you could get back to me.