Australia's climate and environment

The tropical north — Darwin, Cairns, Broome, the Kimberley and Cape York — has two seasons rather than four. The wet season runs roughly November to April, bringing monsoonal rain, extreme humidity and tropical cyclones. The dry season, May to October, is warm, sunny and almost rainless, and is when most travel to the region happens.

The arid and semi-arid interior covers most of the continent: hot days, cold nights, and rainfall that is not merely low but unreliable. Alice Springs can go a year with almost nothing and then receive half its annual average in a week.

The temperate south-east — Sydney, Melbourne, Canberra, Adelaide, Hobart — has four recognisable seasons, with rainfall spread through the year in the east and concentrated in winter towards the south and west. Perth and the south-west corner have a genuinely Mediterranean climate: wet winters, hot dry summers.

Tasmania and the alpine areas of New South Wales and Victoria are the only places with reliable snow, and Australia's alpine zone is small — the highest point, Mount Kosciuszko, is 2,228 metres.

The El Niño–Southern Oscillation is the dominant driver of year-to-year rainfall variability across eastern Australia. In broad terms, El Niño conditions push rainfall away from eastern Australia and raise the risk of drought, heatwaves and severe fire seasons. La Niña conditions do the opposite, raising rainfall and flood risk.

Two other patterns matter. The Indian Ocean Dipole affects rainfall across the south and centre, with a negative phase typically bringing wetter conditions. The Southern Annular Mode shifts the westerly wind belt, changing rainfall in the south of the continent and along the east coast.

These drivers combine, sometimes reinforcing and sometimes cancelling each other, which is why simple El Niño headlines are a poor guide to any particular season. The Bureau of Meteorology publishes a fortnightly climate driver update that is the authoritative source.

Bushfire is the hazard that shapes the most Australian behaviour. The season runs at different times in different states — spring and summer in the south-east, winter and spring in the north — and severity depends on fuel load, drought and wind. The 2019–20 Black Summer fires burned more than 24 million hectares and pushed the national response system to its limits. Every state issues fire danger ratings under the national Australian Fire Danger Rating System, and living in or near bushland means having a written bushfire survival plan.

Flooding causes more insured damage in Australia than any other hazard. Riverine flooding in the eastern states, flash flooding in urban catchments and storm surge on the coast are all significant. Flood risk is highly localised and often not obvious from looking at a property.

Tropical cyclones affect the northern coastline between roughly November and April, with the strongest recorded events in Western Australia and Queensland. Building codes in cyclone regions are correspondingly strict.

Heatwaves kill more Australians than any other natural hazard, and the deaths are concentrated among older people in cities rather than in remote areas. Severe thunderstorms, hail and — much less commonly — earthquakes complete the list.

The Bureau of Meteorology and CSIRO publish a biennial State of the Climate report, which is the authoritative national assessment. Its consistent findings are that Australia's average land temperature has risen about 1.5 °C since national records began in 1910, that the frequency of extreme heat events has increased, that the fire season has lengthened in the south and east, and that rainfall has declined in the south-west and south-east during the cool season while increasing in parts of the north.

Sea surface temperatures around Australia have risen, and the Great Barrier Reef has experienced repeated mass coral bleaching events driven by marine heatwaves — a pattern that was essentially unknown before the late twentieth century.

Australia has legislated an emissions reduction target of 43 per cent below 2005 levels by 2030 and net zero by 2050, under the Climate Change Act 2022. It remains among the highest per-capita emitters in the developed world, largely because of coal-fired electricity and fossil fuel exports, though the share of renewables in the electricity grid has risen very fast — South Australia in particular regularly runs on wind and solar alone for extended periods.

Australia is one of 17 megadiverse countries and has the highest rate of endemism of any: the great majority of its mammals, reptiles, frogs and flowering plants exist nowhere else. Long geological isolation is the reason — the continent separated from Antarctica roughly 30 million years ago and has evolved in its own direction since.

It also has among the worst mammal extinction records in the world. Introduced predators, principally feral cats and foxes, plus habitat clearing and altered fire regimes, have driven more than thirty mammal extinctions since 1788. The Environment Protection and Biodiversity Conservation Act 1999 is the main federal law protecting threatened species and habitats, and has been the subject of repeated critical reviews.

For visitors, the dangerous-animal reputation is largely overstated but not baseless. Deaths from snakes and spiders are rare — antivenoms exist and are effective — while drowning at unpatrolled beaches, heat and road accidents in remote areas cause far more harm. Saltwater crocodiles in the tropical north are the one genuinely serious wildlife risk, and local warning signs there should be treated as absolute.