Whirly, October is usually fairly good too so long as the wet season doesn't arrive early. Do Cairns first in early October if you can then go down south after that. In the tropical north they have what they call the build up. This is the weather pattens changing from the dry season to the wet and is steamy moist atmosphere with towering cu up to 30000' odd.
Many people say the build up is more uncomfortable that the wet especially if you are not aclimatised to it. Mould and mildew grows every where and you are constantly wet with sweat and it is quite energy sapping. It goes for about 4 to 6 weeks then the wet season starts in ernest. Early October you should be fine.