Australia is well known for its gorgeous weather, but ask any traveller who's been stuck in a freezing Melbourne Summer rainstorm, or watched the snow fall in Canberra, and they'll tell you it's not all sunshine lollypops and rainbows.
Australian weather is basically divided into four zones: tropical, sub-tropical, temperate and alpine.
Tropical Australia is everywhere located above the tropic of Capricorn (basically a line drawn roughly through Rockhampton in Queensland, across to Alice Springs in The Northern Territory and Exmouth in Western Australia). There are only two seasons in the tropics, the wet season and the dry season. The wet season takes place around summer (roughly between October to April) as the humidity in the air rises during the day with the extreme heat, condensates (like steam) and then falls in heavy afternoon thunderstorms. In Darwin you can virtually set your watch by the afternoon storms. Temperatures on the coastline hover around 30°-35°C and temperatures inland regularly reach over 40°C.
The dry season lasts between May and September and is characterised by limited rainfall, lower humidity and slightly less hot temperatures (although no one from Europe would be tempted to call them cool). During the day, the coastal regions still regularly reach 30°C and at night it drops below freezing in the inland deserts.
The rest of Queensland, and most of Western Australia experiences increased humidity and storms in Summer but unlike the tropics, they still have four reasonably defined seasons. The weather is still blisteringly hot in summer, but it's perfect in Spring and Autumn and then chilly in Winter, although it only rarely ever freezes, and only then on the highest mountains in the depths of Winter. Daytime temperatures average around 30°C in summer, 25° in Spring and Autumn and 19° in Winter.
The rest of the country (exclusing the small alpine areas) has four fairly well defined seasons. Summers are hot on the mainland and warm in Tasmania. Winters are cold on the mainland and bloody awful in Tasmania. The rest of the year it's pretty nice, although often unpredictable, especially in Melbourne, which is famous for having four seasons in one day. Summer days are usually around 29°, Winter is about 14°, Spring and Autumn hover in the mid 20s. (Although keep in mind it's a huge country, so it's obviously going to be a lot warmer in Byron Bay, NSW, than it is in Hobart, Tasmania, 2000km further south).
I was in a cab in Singapore once and the driver and I were talking about the weather. I was trying to tell him that Australia was generally a pretty hot place. He asked me if it snowed in Australia, and I said that it did in some places. He said Australia wasn't hot then.
While the entire east coast of Australia is girt by a Great Dividing Range of mountains, few of them achieve true alpine status. Even Australia's highest mountain (the 2228m Mt Kosciusko) is a mere hill by Himalayan standards and only sees snow for about half the year. Australia's alpine regions are limited to a cluster of mountains about the size of Ireland at the bottom of the Great Dividing Range on the NSW/Victorian border, and the high peaks in Tasmania. Summer temperatures average about 18°C, Winter is about 2°C in the day and the rest of the year is around 10°C. Snow falls tend to be thicker at the end of Winter, but big thick dumps of snow are limited and only happen a few times a season (and even then they are dustings compared with Canada or even London).
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