The Australian weather conditions are hot during the summer (in most areas) and quite mild during the winter. The tropical regions of Australia north of about Cairns in Queensland and Broome in Western Australia do not really experience cool temperatures even during the winter. You'll find that the temperatures in the southern parts (i.e. the coldest regions) of Australia during the winter are much warmer than most mid-to-high latitude countries such as the UK, Europe, Russia, Canada as well as central and northern China as well as the US. If you're planning to visit Australia and you come from the northern hemisphere, you must remember that the seasons are reversed. In Australia, our winter months are June, July and August.
Furthermore, when I speak of the northern parts of Australia, you can expect the weather to be much more humid and the seasons far less pronounced.