Thank you Gary for the detailed answer!
After a study of weather I have an opinion that it is very similar to what we have here in Ukraine in July. Well, without active tropical cyclons, maybe sometimes hotter, sometimes more/less cloudy, but in general it is similar. And to your knowledge, July-August is astronomical hi-season here, so I won't be disappointed any way if would visit Queensland in November.
The weather isn't actually the biggest problem. For me, the top 3 things to be careful about are: 1) have no problems acquiring visa; 2) have no problems with booking accomodation; 3) be in time for each of 3 consequtive airflights!