Upvote:2
For travel weather, I like to use weatherspark.com. Here is a link for the average weather in Melbourne: http://weatherspark.com/averages/34069/Melbourne-Victoria-Australia
The average temperatures and rainfall, taken from that page, are shown below.
Upvote:4
It's currently summer. Seasons in Australia are the opposite of the northern hemisphere, so if it's winter in the northern hemisphere, it's summer here.
I lived in Melbourne last year, and even when it is summer (and it gets really, really hot) cool changes can come through fast, and temperatures can drop. Bring summer clothes, but you'd be mistaken to not bring one jacket for those rare weather swings.