Brisbane is sub-tropical, lying 27.3° south of the equator, and so enjoys moderate (indeed, perfect) weather all year round. Officially, summer starts December 1st and winter June 1st. Average annual humidity is 50%, with January and February being the wettest months.

Average high Average low
Hottest month is January: 29°C 21°C
Coldest month is July: 21°C 9°C

(For those of you reading this in the US, the conversion from metric to imperial is: 29°C = 85°F, 21°C = 69°F; and 9°C = 49°F.)