Dan,
Can get cold (5c) and can even get snow flurries but none on the ground but also sometimes a nice 15 - 20c days, (I live in the southern part of the continent) but it only really lasts from late June till September then the spring and autumn days are great. Some trees do change colour and lose leaves but not to the degree in Northern America. But the majority of trees are native to Australia (eucalyptus) and thus we have a lot of green around in winter as well.
Having said all that there is always a bed here if you are even inclined to check out the land down under.
Garry