Australia is a large landmass that spans 35° of latitude and so experiences a range of climates. Broadly, the north has a tropical climate, central Australia has a desert climate, and southern Australia has a temperate climate.

There are three climate classification maps described by the Bureau of Meteorology: the choice of system to use depends on the application.

• The most widely used is the Vegetation or Köppen classification map that shows six major groups (identified mainly on native vegetation type) and 27 sub-groups of climate zones (based on seasonal distribution of temperature and precipitation). Example of use: global climate comparison, agricultural long term planning.
• Temperature/humidity zones map shows the climate classified into six zones according to temperature and humidity properties. Example of use: urban or building design
• Seasonal rainfall classification maps show six major climate zones based on the differences between summer and winter rainfall. Example of use: public weather reports, tourism planning.

Australia’s climate is influenced by several large-scale features in the global climate system that affect the weather, especially rainfall, in Australia over different regions and seasons and in different years.

These climate influencers include: El Niño-Southern Oscillation (ENSO) the Indian Ocean Dipole, the Australian monsoon and the Madden-Julian Oscillation, the Southern Annular Mode.

El Niño-Southern Oscillation (ENSO): The winds over the Pacific Ocean close to the Equator typically blow from east to west (and their strength is measured by the Southern Oscillation Index, or SOI). When this typical pattern is disrupted, and the winds weaken or even reverse, the event is described as an El Niño. An El Niño generally brings drier conditions and warmer temperatures to much of eastern Australia. If prolonged, it can lead to drought. El Niño events generally occur every two to seven years – check/update if this is still accurate.

During a La Niña, the typical easterly winds across the Pacific are strengthened, bringing above average rainfall to much of Australia, that may result in flooding. For example, in 2010 and 2011 and 2021, both record breaking periods of rain – check if this is still accurate, were dominated by strong La Niña conditions and damaging floods occurred across several areas in Queensland and NSW.

The Indian Ocean Dipole (IOD) is a measure of the difference in sea surface temperature in the western and eastern equatorial Indian Ocean. When positive, there is cooler than normal water in the tropical eastern Indian Ocean and warmer than normal water in the tropical western Indian Ocean. This pattern is associated with lower rainfall over parts of central and southern Australia. A negative IOD pattern is associated with an increase in rainfall over parts of southern Australia.

The Australian monsoon that influences in northern regions is a key driver of the tropical dry and wet seasons.

The dry season is characterised by southeast trade winds (dry because of their passage over the continent).

The wet season is characterised by moisture-laden northwest monsoonal winds.

During the wet season, the monsoon can be in either an active or an inactive phase. The transition from active to inactive may be associated with the Madden-Julian Oscillation (MJO), an eastward movement of large regions of higher and lower tropical rainfall. The MJO operates on time scales of 30-60 days.

The subtropical ridge is a large circulation feature that affects southern Australia. This is a belt of high pressure that encircles the globe in the middle latitudes.

In the warmer months the ridge is positioned to the south and is associated with stable high pressures and drier climates over southern Australia.

In the cooler months the ridge moves northwards towards the equator, allowing more rain-bearing cold fronts to cross southern Australia.

The Southern Annular Mode (SAM) describes the north-south movement of the westerly wind belt that circles Antarctica.

The Southern Annular Mode (SAM) describes the north-south movement of the westerly wind belt that circles Antarctica.

In the positive phase, the band of westerly winds contracts toward Antarctica and there are higher pressures over southern Australia that can bring stable, dry conditions.

In the negative phase, the band of westerly winds expands towards the Equator and there are more (or stronger) low pressure systems over southern Australia that can bring more storms and rain.

Australia experiences a range of climate extremes, including extreme heat, heavy rainfall, droughts, bushfires, and tropical cyclones. These events have significant impacts on communities, ecosystems, and the economy. A number of these extremes have become more frequent or intense in recent decades, most likely in response to climate change.

A simple definition of tropical cyclones is that they are low pressure systems that form over warm tropical waters when the sea surface temperature is above 26.5 °C and other atmospheric conditions are favourable. Severe tropical cyclones are characterised by catastrophic wind gust speeds, storm surges, extreme rainfall and flooding.

The number of tropical cyclones making landfall in Australia is strongly influenced by ENSO, with more tropical cyclones during La Niña years and fewer in El Niño years. On average Australia experiences about 11 tropical cyclones each year, generally between November and April.