Although Australia experiences wide variations in its climate patterns, the largest part of the country remains under the influence of a desert of semi-arid type, with 40% of its landmass covered by sand dunes. The northern Australia has a tropical climate – parts of it tropical rainforests, part grasslands, and part desert – and only the south-east and south-west corners lie in the region of temperate climates, enjoying moderately fertile soil.
Rainfall patterns also change dramatically, although because of the influence of the El Niño-Southern Oscillation draughts are frequent and prolonged and dust storms occasionally blanket whole regions and – in extreme cases – parts of several states. The country is also open to occasional attacks by large tornadoes.
Australia's tropical/subtropical location and cold waters off the western coast make most of western Australia a hot desert with aridity a marked feature of a greater part of the continent. These cold waters produce precious little moisture needed on the mainland. A 2005 study by Australian and American researchers[1] investigated the desertification of the interior, and suggested that one explanation was related to human settlers who arrived about 50,000 years ago. Regular burning by these settlers could have prevented monsoons from reaching interior Australia.
The rainfall patterns across Australia are highly seasonal. Compared to the Earth's other continental landmasses Australia is very dry. More than 80 percent of the continent has an annual rainfall of less than 600 millimetres; only Antarctica receives less rainfall than Australia. From one extreme to another, parts of the far North Queensland coast annually average over 4000 mm, with the Australian annual record being 12461 mm, set at the summit of Mount Bellenden Ker in 2000. There are four main factors that contribute to the dryness of the Australian landmass:
Cold ocean currents off the west coast
Low elevation of landforms
Dominance of high-pressure systems
Shape of the landmass
Low rate of evaporation from this very cool body of water result in little evaporation occurring. As a result, rain clouds are sparsely formed and very rarely do they form long enough for a continuous period of rain to be recorded. Australia's arid/semi-arid zone extends to this region. The absence of any significant mountain range or area of substantial height above sea level, results in very little rainfall caused by orographic uplift. In the east the Great Dividing Range limits rain moving into inland Australia. Australia has a compact shape and no significant bodies of water penetrate very far inland. This is important because it means that moist winds are prevented from penetrating to inland Australia, keeping rainfall low.
In Australia, snow can fall in the mountains of Victoria, Australian Capital Territory, New South Wales and Tasmania. There is a regular snow season in several areas which have seasonal ski tourism industries. Sometimes snow has even been reported in the mountains of South Australia, Western Australia and Queensland though this is very rare.
Snow at sea level has been recorded on mainland Australia but has happened more times in Tasmania, some of the snow at sea level has fallen in the off season like summer. Snow has fallen nearly everywhere in Tasmania, though it is rare to fall in the north coast at sea level.
The occasional cold snap, caused by cold air drifting north from Antarctica, can cause significant snowfall in rural areas, as well as major cities such as Hobart, Melbourne's outer mountain suburbs, Canberra and Sydney. Such occasions are rare, but have occurred in 1951, 1986 and 2005
