I was wondering what weather in Cairns and Sydney would be mid-late September?

Was checking tonight and found availability for Business Award flights on Delta for 110,000 miles and American for 80,000 miles, for multiple dates in September 2017.

Looking at leaving on Sept 14, which gives me arriving into Cairns on Sept 16 then 5 nights there then flying to Sydney for 7 nights and returning Sept 28.