Storm In Sydney, September 2009, Australia

The climate of Australia is significantly influenced by ocean currents, including the Indian Ocean Dipole and the El Niño-Southern Oscillation, which is correlated with periodic drought, and the seasonal tropical low pressure system that produces cyclones in northern Australia. These factors induce rainfall to vary markedly from year to year. Much of the northern part of the country has a tropical predominantly summer rainfall (monsoon) climate. Just under three quarters of Australia lies within a desert or semi-arid zone. The southwest corner of the country has a Mediterranean climate. Much of the southeast (including Tasmania) is temperate.
Environment
Although most of Australia is semi-arid or desert, it includes a diverse range of habitats from alpine heaths to tropical rainforests, and is recognised as a megadiverse country. Because of the continent's great age, extremely variable weather patterns, and long-term geographic isolation, much of Australia's biota is unique and diverse. About 85 per cent of flowering plants, 84 per cent of mammals, more than 45 per cent of birds, and 89 per cent of in-shore, temperate-zone fish are endemic. Australia has the greatest number of reptiles of any country, with 755 species.