Every nationality except New Zealanders need visas.
Tourists visas are valid for six months.
The North is beautifully green and free of tourists at this time. The weather is reasonably mild wherever you are, and spring brings out the wildflowers in the outback. This time is beautiful in Canberra and in the Victorian Alps. This is a good time to visit Queensland or the outback. In the Northern Territory cane toads, possibly the ugliest toads in the world, are spreading into the pristine Kakadu National Park.