And watch out for our ferocious bears!!! 
yeah, those drop bears can be pretty scary...
Anyway, elspeth, I'm not too sure about Cairns, coming from the other side of Australia, but it's usually pretty humid up there, and hot even in winter.
When you say next summer, what months are you thinking of? I'm not sure where you're from so I don't know if you're talking about our summer, your summer, etc.
If it happens to be our summer, bring shorts and singlets, thongs (the footwear kind

), a hat, sunnies, and watch out for snakes - in summer they move faster. It will be hot. Very very hot.
Don't let all of this put you off...Australia really is an easy place to live in. I very rarely encounter dangerous species. Enjoy yourself.
