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HEY MOM?Australia]] is desert or semi-arid – 40% of the landmass is covered by sand dunes. Only the south-east and south-west corners have a temperate climate and moderately fertile soil. The northern part of the country has a tropical climate: part is tropical rainforests, part grasslands, and part desert.

Rainfall is highly variable, with frequent droughts lasting several seasons thought to be caused in part by the El Niño-Southern Oscillation. Occasionally a duststorm will blanket a region or even several states and there are reports of the occasional large tornado. Rising levels of salinity and desertification in some areas is ravaging the landscape.

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 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.

Regions

South-eastern temperate region

The south-eastern temperate zone spans from Ceduna in South Australia along the coast to the town of Forster in New South Wales, the climate in this region is also referred to as an oceanic climate. The region's climate is typified by warm summers and mild winters, with temperatures averaging close to 20°C. Statistically the warmest month is January and the coldest month is July, though it is rare that either will provide extreme temperatures on either end of the spectrum, however this is not the case further inland. Rainfall is evenly spread between summer and winter though is generally heavier in the first half of the year. Although the region does not suffer from natural phenomena such as cyclones, it is affected by the El Niño Southern Oscillation with drought and during El Niño and storms and flooding in periods of La Niña. The region’s climate has also been affected by global warming in recent times, with January 2006 becoming the hottest month on record and the tenth consecutive month above median temperature.

Central arid region

Deserts of Australia cover a large portion of the land in Australia. Most of the deserts lie in the central and north-western part of the country. Just under three quarters of Australia lies within a desert or semi-arid zone. The size of the deserts in Australia combined is 2.3 million square km (1.3 million square miles), and occupies 44% of the continent. The average annual rainfall is low, ranging from 200 to 250 mm (7.9 to 9.8 in) per year. Thunderstorms are relatively common in the region, with an average of 15 - 20 thunderstorms per annum. Summer daytime temperatures range from 32 to 40 °C (90 to 104 °F). In winter, this falls to 18 to 23 °C (64 to 75 °F). Snow never falls in any desert.'

States and Territories

Australian Capital Territory

Because of its elevation (650 m) and distance from the coast, the Australian Capital Territory experiences four distinct seasons, unlike many other Australian cities whose climates are moderated by the sea. Canberra is notorious for hot, dry summers, and cold winters with occasional fog and frequent frosts. Many of the higher mountains in the territory’s south-west are snow-covered for at least part of the winter. Thunderstorms can occur between October and March, and annual rainfall is 623 millimetres (24.5 in), with rainfall highest in spring and summer and lowest in winter.

The highest maximum temperature recorded in the ACT was 42.8 °C (109.0 °F) at Acton on 11 January 1939. The lowest minimum temperature was −14.6 °C (5.7 °F) at Gudgenby on 11 July 1971.

New South Wales

The highest maximum temperature recorded was 50.0 °C (122.0 °F) at Wilcannia in the state's west on 11 January 1939. The lowest minimum temperature was −23.0 °C (−9.4 °F) at Charlotte Pass on 29 June 1994 in the Snowy Mountains. This is also the lowest temperature recorded in whole of Australia excluding Australian Antarctic Territory.

Northern Territory

The Northern Territory has two distinctive climate zones. The northern end, including Darwin, has a tropical savanna climate (Köppen Aw) with high humidity and two seasons, the wet (November to April) and dry season (May to October). During the dry season nearly every day is warm and sunny, and afternoon humidity averages around 30%. There is very little rainfall between May and September. In the coolest months of June and July, the daily minimum temperature may dip as low as 14 °C (57 °F), but very rarely lower, and frost has never been recorded. The wet season is associated with tropical cyclones and monsoon rains. The majority of rainfall occurs between December and March (the southern hemisphere summer), when thunderstorms are common and afternoon relative humidity averages over 70% during the wettest months. On average more than 1,570 mm (62 in) of rain falls in the north.

The central region is the desert centre of the country, which includes Alice Springs and Ayers Rock, and is semi-arid with little rain usually falling during the hottest months from October to March. Central Australia receives less than 250 mm (9.8 in) of rain per year. The highest maximum temperature recorded in the territory was 48.3 °C (118.9 °F) at Finke on 2 January 1960. The lowest minimum temperature was −7.5 °C (18.5 °F) at Alice Springs on 12 July 1976.

Queensland

Because of its size, there is significant variation in climate across the state. Low rainfall and hot summers are typical for the inland west, a monsoonal 'wet' season in the far north, and warm temperate conditions along the coastal strip. Inland and in southern ranges low minimum temperatures are experienced. The climate of the coastal strip is influenced by warm ocean waters, keeping the region free from extremes of temperature and providing moisture for rainfall.

There are five predominate climatic zones in Queensland, based on temperature and humidity:

• hot humid summer (far north and coastal)
• warm humid summer (coastal elevated hinterlands and coastal south-east)
• hot dry summer, mild winter (central west)
• hot dry summer, cold winter (southern west)
• temperate - warm summer, cold winter (inland south-east, e.g. Granite Belt)

However, most of the Queensland populace experience two weather seasons: a "winter" period of rather warm temperatures and minimal rainfall and a sultry summer period of hot, sticky temperatures and higher levels of rainfall. The highest maximum temperature observed in the state is 49.5 °C (121.1 °F) at Birdsville on 24 December 1972 (The temperature of 53.1 °C (127.6 °F) at Cloncurry on 16 January 1889 is not considered official; the figure quoted from Birdsville is the next highest, so that record is considered as being official). The lowest minimum temperature is −11.0 °C (12.2 °F) at Stanthorpe on 4 July 1895

South Australia

South Australia's mean temperature range is 29 °C (84 °F) in January and 15 °C (59 °F) in July. Daily temperatures in parts of the state in January and February can be up to 48 °C (118 °F).

The highest maximum temperature was recorded as 50.7 °C (123.3 °F) at Oodnadatta on 2 January 1960, which is the highest official temperature recorded in Australia. The lowest minimum temperature was −8.0 °C (17.6 °F) at Yongala on 20 July 1976

Tasmania

Tasmania has a cool temperate climate with four distinct seasons. Summer lasts from December to February when the average maximum sea temperature is 21 °C (70 °F) and inland areas around Launceston reach 24 °C (75 °F). Other inland areas are much cooler with Liawenee, located on the Central Plateau, one of the coldest places in Australia with temperatures in February ranging between 4 °C (39 °F) to 17 °C (63 °F). Autumn lasts between March and May and experiences changeable weather, where summer weather patterns gradually take on the shape of winter patterns.

The winter months are between June and July and are generally the wettest and coolest months in the state, with most high lying areas receiving considerable snowfall. Winter maximums are 12 °C (54 °F) on average along coastal areas and 3 °C (37 °F) on the central plateau, thanks to a series of cold fronts from the Southern Ocean. Spring is a season of transition, where winter weather patterns begin to take the shape of summer patterns. Although snowfall is still common up until October. Spring is generally the windiest time of the year with afternoon sea breezes starting to take effect on the coast.

Rainfall in Tasmania follows a complicated pattern rather analogous to that found on large continents at the same latitude in the northern hemisphere. On the western side rainfall increases from around 1,458 millimetres (57.4 in) at Strahan on the coast up to 2,690 millimetres (106 in) at Cradle Valley in the highlands.

There is a strong winter maximum in rainfall: January and February typically averages between 30-40% the rainfall of July and August, though even in the driest months rain usually falls on every second day and the number of rainy days per year is much greater than on any part of the Australian mainland. Further east in the Lake Country, annual rainfall declines to around 900 millimetres (35 in), whilst in the Midlands, annual rainfall is as low as 450 millimetres (18 in) at Ross and generally below 600 millimetres (24 in). The eastern part of Tasmania has more evenly distributed rainfall than in the west, and most months receive very similar averages.

The densely populated northern coast is much drier than the western side, with annual rainfall ranging from 666 millimetres (26.2 in) in Launceston to 955 millimetres (37.6 in) in Burnie in the north west and 993 millimetres (39.1 in) in Scottsdale located further to the east. Most rain falls in winter, and in summer the average can be as low as 31 millimetres (1.2 in) per month in Launceston. The east coast is wetter than the Midlands, with an average annual rainfall ranging from 775 millimetres (30.5 in) in St. Helens to around 640 millimetres (25 in) in Swansea. Here the rainfall is evenly distributed over the year but can be very erratic as heavy rainfalls from the warm Tasman Sea are quite frequent. Whereas a three-day fall of 125 millimetres (4.9 in) occurs only once every fifty years on the north coast, it occurs on average once every four or five years around Swansea and Bicheno, and on 7 June-8 June 1954, there were many falls as large as 230 millimetres (9.1 in) in two days in that area. The east coast is sometimes called the "sun coast" because of its sunny climate.

Several sections of inland Tasmania, together with Flinders Island, were declared drought-affected areas by the state government in 2007.

Victoria

Victoria has a varied climate despite its small size. It ranges from semi-arid and hot in the north-west, to temperate and cool along the coast. Victoria's main land feature, the Great Dividing Range, produces a cooler, mountain climate in the centre of the state.

Victoria's southernmost position on the Australian mainland means it is cooler and wetter than other mainland states and territories. The coastal plain south of the Great Dividing Range has Victoria's mildest climate. Air from the Southern Ocean helps reduce the heat of summer and the cold of winter. Melbourne and other large cities are located in this temperate region. The Mallee and upper Wimmera are Victoria's warmest regions with hot winds blowing from nearby deserts. Average temperatures top 30 °C (86 °F) during summer and 15 °C (59 °F) in winter. Victoria's highest maximum temperature of 47.9 °C (118.2 °F) was recorded in Avalon on 7 February 2009. The Victorian Alps in the northeast are the coldest part of Victoria. The Alps are part of the Great Dividing Range mountain system extending east-west through the centre of Victoria. Average temperatures are less than 9 °C (48 °F) in winter and below 0 °C (32 °F) in the highest parts of the ranges. The state's lowest minimum temperature of −12.8 °C (9.0 °F) was recorded at Mount Hotham on 13 August 1947.

Victoria is the wettest Australian state after Tasmania. Rainfall in Victoria increases from north to south, with higher averages in areas of high altitude. Median annual rainfall exceeds 1,800 millimetres (71 inches) in some parts of the northeast but is less than 250 millimetres (10 inches) in the Mallee. Rain is heaviest in the Otway Ranges and Gippsland in southern Victoria and in the mountainous northeast. Snow generally falls only in the mountains and hills in the centre of the state. Rain falls most frequently in winter, but summer precipitation is heavier. Rainfall is most reliable in Gippsland and the Western District, making them both leading farming areas. Victoria's highest recorded daily rainfall was 375 millimetres (14.7 in) at Tanybryn in the Otway Ranges on 22 March 1983.

• Average January temperatures:
  Victoria's north is always hotter than coastal and mountainous areas.
• Average July temperatures:
  Victoria's hills and ranges are coolest during winter. Snow also falls there.
• Average yearly precipitation:
  Victoria's rainfall is concentrated in the mountainous north-east and coast.

Western Australia

The southwest coastal area is relatively temperate and was originally heavily forested, including large stands of the karri, one of the tallest trees in the world. This agricultural region of Western Australia is in the top nine terrestrial habitats for terrestrial biodiversity, with a higher proportion of endemic species than most other equivalent regions. Thanks to the offshore Leeuwin Current the area numbers in the top six regions for marine biodiversity, containing the most southerly coral reefs in the world.

Average annual rainfall varies from 300 millimetres (12 in) at the edge of the Wheatbelt region to 1,400 millimetres (55 in) in the wettest areas near Northcliffe, but in the months of November to March evaporation exceeds rainfall, and it is generally very dry. Plants must be adapted to this as well as the extreme poverty of all soils. A major reduction in rainfall has been observed, with a greater number of rainfall events in the summer months.

The central four-fifths of the state is semi-arid or desert and is lightly inhabited with the only significant activity being mining. Annual rainfall averages about 200 to 250 millimetres (8–10 in), most of which occurs in sporadic torrential falls related to cyclone events in summer months.

An exception to this is the northern tropical regions. The Kimberley has an extremely hot monsoonal climate with average annual rainfall ranging from 500 to 1,500 millimetres (20–60 in), but there is a very long almost rainless season from April to November. Eighty-five percent of the state's runoff occurs in the Kimberley, but because it occurs in violent floods and because of the insurmountable poverty of the generally shallow soils, the only development has taken place along the Ord River.

Occurrence of snow in the state is rare, and typically only in the Stirling Range near Albany, as it is the only mountain range far enough south and with sufficient elevation. More rarely, snow can fall on the nearby Porongurup Range. Snow outside these areas is a major event; it usually occurs in hilly areas of southwestern Australia. The most widespread low-level snow occurred on 26 June 1956 when snow was reported in the Perth Hills, as far north as Wongan Hills and as far east as Salmon Gums. However, even in the Stirling Range, snowfalls rarely exceed 5 cm (2.0 in) and rarely settle for more than one day.

The highest observed maximum temperature of 50.5 °C (122.9 °F) was recorded at Mardie, Pilbara, 61.6 kilometres (38.3 miles) from Barrow Island on 19 February 1998. The lowest minimum temperature recorded was −7.2 °C (19.0 °F) at Eyre Bird Observatory, 49 km (30 mi) south of Cocklebiddy on 17 August 2008.

Natural hazards and disasters

Bushfires

Climatic factors contribute to Australia's high incidence of bushfires, particularly during the summer months. Low relative humidity, wind and lack of rain can cause a small fire, either man-made or caused naturally by lightning strikes, to spread rapidly over large distances. Low humidity, the heat of the sun and lack of water cause vegetation to dry out becoming a perfect fuel for the fire. High winds fan the flames, increasing their intensity and the speed and distance at which they can travel.

Many of the worst bushfires in eastern Australia, such as the 1983 Ash Wednesday fires, accompany El Niño-Southern Oscillation events which tend to cause a warm, dry and windy climate. The worst bushfires in Australian history occurred in February 2009,(Black Saturday) in which the human death toll exceeded 200, and over 2000 homes were lost.

Global warming

Global warming is causing climate change which is predicted by the CSIRO to have significant effects on the climate of and extreme weather events in Australia. It is predicted that the Great Barrier Reef and reefs surrounding Lord Howe Island could be killed as a result of the rise in water temperature forecast by the IPCC Fourth Assessment Report. The Murray River, Darling River Coorong and Macquarie Marshes are all at risk from decreased rainfall from climate change.

Coastal communities face risks from sea level rise, albeit over a long period of time based on current estimates of the IPCC Fourth Assessment Report. The Gold Coast, being built on sand and with many canal developments, could be considered particularly at risk. Suburbs of Sydney like Drummoyne and Concord on rivers like the Parramatta River face risks of inundation of low lying areas such as parks (such as Timbrell Park and Majors Bay Reserve) reclaimed from mudflats at the heads of bays, or massive expenses in rebuilding seawalls to higher levels.

Currently, there are several environmental movements and campaigners advocating for action on climate change. One such campaign is "The Big Switch", Australia's largest community climate change campaign.

New projections for Australia's changing climate includes:

• droughts are likely to become more frequent, particularly in the south-west
• evaporation rates are likely to increase, particularly in the north and east
• high-fire-danger weather is likely to increase in the south-east
• sea levels will continue to rise

Drought

Drought in Australia is defined by rainfall over a three month period being in the lowest ten percent of amounts having been recorded for that region in the past. This definition takes into account that low rainfall is a relative term and rainfall deficiencies need to be compared to typical rainfall patterns including seasonal variations. Specifically drought in Australia is defined in relation to a rainfall deficiency of pastoral leases and is determined by decile analysis applied to a certain area.

Historical climatic records are now sufficiently reliable to profile climate variability taking into account expectations for regions. State Governments are responsible for declaring a region drought affected and the declaration will take into account factors other than rainfall.

Cyclones

Australia is affected by tropical cyclones which primarily occur between December and April. A few cyclones are known to impact the coast in November and May as well. The region between Broome and Exmouth are most prone to cyclones. Tropical cyclones are known to bring destructive winds, heavy rain with flooding creating storm surges along the coast, causing inundation in low lying areas. The strongest Australian region cyclone was Cyclone Monica in 2006 which had wind gusts in excess of 350 km/h. Cyclones can also move inland, decaying to a rain depression, dumping heavy rain in these areas and causing flooding.

The worst cyclones of Australia have caused billions of dollars of damage and many deaths. Cyclone Tracy crossed directly over Darwin in 1974, 71 people were killed and caused nearly $5 billion (2005 AUD) in damage. Cyclone Mahina in 1899 brought a storm surge to Far North Queensland reaching 13 metres high, and causing 400 deaths.

Blizzards

Blizzards are not a common thing in Australia's mainland though blizzards have occurred in mountainous areas, including the Snowy Mountains in New South Wales and Victoria. When blizzards do occur they are most likely to affect the Tasmanian Highlands and particularly Mount Wellington, which towers over the Tasmanian capital Hobart. Blizzards do not affect any towns or cities, because no populated areas are located in the mountains except skiing resorts.

See also

• Indigenous Australian seasons
• List of wettest known tropical cyclones in Australia

References

1. Miller G, Mangan J, Pollard D, Thompson S, Felzer B, et al. (2005) Sensitivity of the Australian Monsoon to insolation and vegetation: Implications for human impact on continental moisture balance. Geology: Vol. 33, No. 1 pp. 65–68
2. Heavy snow in southern Australia, BBC News, 10 August 2005.
3. Drought-hit farmers turn water thieves in tradition of Ned Kelly, The Guardian, 27 November 2002.
4. Two dead as floods swamp eastern Australia, Planet Ark, world environment news, 13 March 2001.
5. NSW January 2006: Warmest month ever recorded, Australian Bureau of Meteorology, 1 February 2006.
6. Loffler, Ernst (1983). Australia:Portrait of a continent. Richmond, Victoria: Hutchinson Group (Australia). p. 37. ISBN 0091304601. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
7. Australian Bureau of Statistics, 2002 Yearbook of Australia, retrieved 22 July 2007
8. "World Temperature Extremes".
9. "Summary statistics Darwin Airport". Bureau of Meteorology. 2009-07-15. Retrieved 2009-07-26.
10. "Summary statistics Alice Springs Airport". Bureau of Meteorology. 2009-07-16. Retrieved 2009-07-26.
11. "CHAPTER 7: Introduction to the Atmosphere". physicalgeography.net. Retrieved 2008-07-15.
12. World Extremes, http://members.iinet.net.au/~jacob/worldtp.html
13. Australian Government, Bureau of Meterology - Climate of Queensland
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16. "World temperature extremes". 2005-10-17. Retrieved 2006-05-28. {{cite web}}: Check date values in: |date= (help)
17. "Climate of Launceston". Australian BOM. Retrieved 2009-01-01.
18. "Tasmania Climate". World 66. Retrieved 2009-01-01.
19. "Cradle Valley Climate". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
20. "Burnie Climate". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
21. "Scottsdale Climate". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
22. "St Helens Climate". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
23. "Swansea Climate". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
24. "Climate of Tasmania". T Change. Retrieved 2009-01-01.
25. "Midlands Drought area" (PDF). Tasmanian Government. Retrieved 2009-01-01.
26. "Hobart Climate Statistics". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
27. "Launceston Climate Statistics". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
28. "Devonport Climate Statistics". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
29. "Strahan Climate Statistics". Australian Government Bureau of Meteorology. Retrieved 2009-01-01.
30. "Summary statistics Melbourne Regional Office". Bureau of Meteorology. 2009-07-16. Retrieved 2009-07-26.
31. "Summary statistics Mildura Airport". Bureau of Meteorology. 2009-07-16. Retrieved 2009-07-26.
32. Snow in Western Australia: About Snow in WA, retrieved 4 February 2007
33. "Marble Bar heatwave, 1923-24". Bureau of Meteorology. Retrieved 2008-10-25.
34. "Media Release: Eyre sets new record low temperature for WA". Bureau of Meteorology. 18 August, 2008. Retrieved 2008-10-25. {{cite web}}: Check date values in: |date= (help)
35. Weather and Fire, Bureau of Meteorology (Australia). Retrieved 2007-05-02.
36. Australian Climate Extremes - Fire, Bureau of Meteorology (Australia). Retrieved 2007-05-02.
37. http://www.cnn.com/2009/WORLD/asiapcf/02/08/australia.wildfires/index.html
38. CSIRO's "Climate Change Impacts on Australia and the Benefits of Early Action to Reduce Global Greenhouse Gas Emissions"
39. The Big Switch, Australia's largest community climate change campaign
40. New Projections For Australia's Changing Climate
41. ^ "Drought". Climate Glossary. Bureau of Meteorology. 2006. Retrieved 2006-11-13.
42. Tapper, Nigel. & Hurry, Lynn. (1993) Australia's Weather Patterns: An Introductory Guide. Pages 51 -57. Dellasta. ISBN 1-875627-14-6
43. "Our Natural Resources at a Glance - Climate". Department of Agriculture, Fisheries and Forestry (Australia). 2006. Retrieved 2006-11-13.
44. "When is the cyclone season?". Bureau of Meteorology (Australia). 2007. Retrieved 2007-05-10.
45. "What is the most cyclone-prone region in Australia?". Bureau of Meteorology (Australia). 2007. Retrieved 2007-05-10.
46. "Bureau-Bureau of Meteorology - Surviving Cyclones". Bureau of Meteorology (Australia). 2007. Retrieved 2007-05-10.

External links

• Australian Bureau of Meteorology - Climate Information
• The Big Switch, Australia's largest community climate change campaign

• Climate of Australia