Believe it or not, Melbourne can get pretty hot over the summer months. The temperature hit 40 degrees celsius the other day.
Our backyard hive gets a fair bit of afternoon sun during summer. There's a large water tank to the right of the picture below (about 1 metre from the side of the hive) which provides some shade but when the sun is high in the sky the hive is in full sun from around 11 am. It's completely shaded by 3 pm but that still leaves 4 hours in the middle of the day where it catches a lot of sun. Relocating the hive elsewhere in the garden isn't really an option as we don't have another suitable spot. There is always plenty of water available for our bees, however on hot days we also install some temporary shade to assist the 'girls' in their efforts to cool the hive.
It's nothing fancy. On the night before we place 2 bricks on top of the lid, then a large piece of cardboard, followed by 2 more bricks to secure it. This makes a kind of cardboard umbrella. The first layer of bricks allows air flow between the lid and the cardboard which assists in cooling. You'll have to excuse the dark photo below - it was taken in the evening after the cardboard was installed.
It's certainly not a pretty setup..........but it helps, and that's what matters.