3，4月份澳洲 early Fall, 7,8 Winter

Southern Hemisphere has the exact opposite season from Northern Hemisphere.

Here comes your Encyclopedia:

Australia is a big country - it depends where you want to go in Australia, to determine when you want to go.

If your destinations include Queensland, esp Great Barrier Reef, then Fall and Winter is the ideal season. Summer would be like hell - very hot and very humid and rains almost everyday. (there is a rainforest not too far from Cairns)

On the other hand, Hobart (Tasminia Island) and Melbourne, would be quite cold in their Winter time.

Last time we were in Melbourne Zoo, all the animals were in hiding because of the coldness. The zoo even gave rags to those Chimpanzees and they know how to put the rags on their bodies to keep themselves warm! The animals must look at us few visitors thinking how dumb these human beings are, to come out in such temperature! It was like 27F but felt much colder due to windchill factor.

Inland, like the Uluru (Ayers Rock) areas, think death valley climate. Since you enjoy climbing, this probably is your must go.

To compromise, Spring or Fall would be the best seasons to go.