Dear moonlight, I used to live in Sydney and I know exactly what you are talking about in regards of the weather over there.
There are a few personal favourites which I have worn a lot when I was residing there.
Kenzo Flower - wild hawthorn, bulgarian rose, parma violet, cassia, hedione, white musk and vanilla
Kenzo Parfum D'ete is a green, floral fragrance. Hyacinth, freesia, narcissus, peony, rose and jasmine are combined with musk and amber. (This is fresher and greener than Kenzo Flower)
Byblos by Byblos - violet, grapefruit, honeysuckle, and spicy notes of pepper and musk. This is a sharp floral. Not sure if this is available in Australia. This has an amazing sillage and quite long lasting.
Annick Goutal's Folavril - A mango, jasmine, Boronia flower, and spicy tomato leaf blend. I got my first bottle from David Jones City Store. I am not sure if they still carry it.
Hope this helps, good luck!