Well it's a bit complicated mate, latitude is only part of it. Canberra is actually the coldest of the Capitals but also one the hottest. Hot and dry in summer, frequently well over 40C (104F). That's what happens when you're 100 miles from the coast and 2000 ft above sea level. Adelaide and Melbourne are often hotter though. Bateman's Bay is way more temperate and doesn't get the extremes of Canberra; it's a bit closer to Sydney's weather. Brisbane has more of a sub-tropical climate. Rarely gets down to single figures in winter and not as hot in summer but much more humid.
Here endeth the lesson.