Drought
Rainfall deficiencies and water availability

Driest October since 2002

For Australia as a whole, October rainfall was 65.4% below the 1961–1990 average, the fifth-driest on record for October since the national dataset began in 1900, and the driest since 2002.

All states and territories except Victoria had below average rainfall for October. For Western Australia, it was the driest October on record since 1900, with statewide rainfall 83.5% below average. For Queensland, it was the sixth-driest October on record, 83.8% below average, while for South Australia it was 76.4% below average.

October rainfall was in the lowest 10% of historical observations (compared with all Octobers since 1900) for south-western and large parts of eastern Western Australia, for most of the western Northern Territory and parts of the Top End, much of the south-eastern quarter of Queensland as well as areas of the Cape York Peninsula, and South Australia's North West Pastoral and Lower Eyre Peninsula districts. October rainfall was the lowest on record for parts of northern Wide Bay and Burnett and southern Central Highlands and Coalfields districts in Queensland. For northern Australia (north of 26°S), October was the driest start to its wet season period (October to April) since 2002.

October rainfall was above average for most of eastern Victoria extending into adjacent parts of New South Wales.

For Australia as a whole, August to October rainfall was 61.2% below the 1961–1990 average. The area-average total of 22.63 mm was the lowest 3-month total for any such period since 1900 (previous record was 23.68 mm in July–September 1994). Most of south-eastern Queensland had lowest on record rainfall for the period. Rainfall was below average for most of the country except for parts of central and eastern Victoria, the north tropical Queensland coast and some inland areas of Western Australia.

For the cool season (April to October), area-averaged rainfall across southern Australia (south of 26°S) was 152.9 mm, 33% below the 1961–1990 average. Rainfall was below average for much of western and southern Western Australia, South Australia's coastal areas extending inland, Victoria's South West, Central and East Gippsland districts, Tasmania, and the eastern two-thirds of New South Wales and Queensland. Above average rainfall was limited to eastern parts of Western Australia and northern South Australia extending into the Northern Territory.

For the 3-month period since August 2023, areas of rainfall deficiencies have developed across most of the Northern Territory, into South Australia, northern Tasmania, along the south-west and southern coast as well as much of eastern Australia, including south-eastern Queensland.

For the 6-month period since May 2023, there are areas of rainfall deficiency in all states and territories, including most of south-west Western Australia and along much of the south-east of Australia.

Large parts of these areas have had rainfall deficiencies for at least 11 months since December 2022, particularly along the coast in Western Australia and south-eastern Australia, extending inland in northern New South Wales and southern Queensland.

Since September, areas of deficiency have generally expanded and become more severe in south-west Western Australia, south-eastern Queensland, and parts of the Top End in the Northern Territory and far north Queensland. Deficiencies eased in southern Victoria and eastern Tasmania.

The long-range forecast released on 2 November 2023 indicates that below median rainfall for November 2023 to January 2024 is likely to very likely (60% to greater than 80% chance) for northern, western and southern Australia. Above average rainfall is likely (close to 60% chance) for small areas around the Queensland–New South Wales border.

State of the Climate 2022 reported a long-term shift towards drier conditions across the south-west and south-east of Australia, particularly during the cool season months of April to October. This is due to a combination of natural variability on decadal timescales and changes in large-scale circulation caused by an increase in greenhouse gas emissions. Since the 1990s, in the absence of strong 'wet' drivers, cool season (April to October) rainfall in southern Australia has generally been lower than average.

Deficiencies for the 3 months since August 2023

For the 3-month period since August 2023, areas of severe or serious rainfall deficiencies (totals in the lowest 5% or 10% of periods since 1900) have developed across most of the Northern Territory, into South Australia, along the south-west and southern coast, northern Tasmania and much of eastern Australia. Most of south-eastern Queensland had lowest on record rainfall for the period.

This 3-month period includes the last 2 months of the northern dry season (May to September), where rainfall totals in the Northern Territory away from the coast can be small (0–50 mm). However, for northern Australia (north of 26°S), October was also the driest start to its wet season period (October to April) since 2002. In contrast, areas of southern Australia affected by rainfall deficiencies were in the last three months of the southern cool season (April to October). These regions typically have 100–300 mm during the August to October period (and higher in elevated areas), so the current rainfall deficiencies are relatively significant. Along and east of The Great Divide, rainfall in the south-east of the country was generally 100–200 mm below average for the 3-month period.

Deficiencies for the 6 months since May 2023

For the 6-month period since May 2023, areas of severe or serious rainfall deficiencies (totals in the lowest 5% or 10% of periods since 1900) extend across most of the south-west of Western Australia, along the West Coast to the Mid North districts in South Australia, parts of south-central and eastern Victoria, part of the central-east coast of Tasmania, along eastern New South Wales and inland across the northern quarter of the state, and most of south-eastern Queensland. In the north, a band of deficiencies runs from the Tiwi Islands to Groote Eylandt in the Northern Territory and extends into Far North Queensland.

During October, rainfall deficiencies have generally intensified or expanded, particularly in south-west Western Australia and south-eastern Queensland. Large areas of lowest on record rainfall extend over much of the Gascoyne district in Western Australia, and from Wide Bay and Burnett, into the Darling Downs and Granite Belt districts and part of the Maranoa and Warrego district in Queensland.

Deficiencies for the 11 months since December 2022

For the 11-month period starting December 2022, country with severe or serious rainfall deficiencies (totals in the lowest 5% or 10% of periods since 1900) includes areas along the coast of Western Australia between Carnarvon and Busselton, the Eucla district, and some inland areas in the south-west. In eastern Australia, large areas of deficiency are concentrated in the south-eastern corner of Queensland and north-eastern New South Wales. Small areas of deficiency fringe the New South Wales and Victorian east coast, and isolated pockets occur in South Australia and south-east Tasmania.

Since September the extent and severity of 11-month rainfall deficiency areas increased in south-west Western Australia and south-eastern Queensland but reduced in Victoria and eastern Tasmania.

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Below average soil moisture across most of Australia

October root-zone soil moisture (soil moisture in the top 100 cm) was below to very much below average (driest 30 to 10% of years since 1911) across most of Australia. It was particularly dry in southern and eastern Australia including north and east Tasmania, as well as some areas in the Northern Territory. Large areas of lowest on record soil moisture have developed in south-eastern Queensland.

Since September, soil moisture decreased across most of Australia, except for small areas that received rainfall from storms, most notably in south-eastern Victoria.

High evaporative stress across southern Western Australia and south-eastern Queensland

Evaporative stress for the 4 weeks ending 1 October 2023 is elevated (index is negative) across most of Australia away from the north. Southern exceptions include a band across the far south-east, including most of eastern Victoria and into central Tasmania.

Compared to last month, the evaporative stress index has increased in intensity in southern Western Australia, south-eastern Queensland, eastern Tasmania, and in the north of Australia.

See the journal publication for further details on calculation and use of evaporative stress index in drought monitoring.

• For Australia as a whole, October rainfall was 65% below the 1961–1990 average, the fifth-driest October on record (since 1900) and the driest since 2002.
• Rainfall in October was below average for most of Australia, and the driest on record for Western Australia.
• Australian August–October 2023 rainfall was 61.2% below the 1961–1990 average, and the area-average total of 22.63 mm makes it Australia's driest 3-month period on record for any such period since 1900.
• Most of south-eastern Queensland had lowest on record August–October rainfall and large areas of 3-month rainfall deficiencies have also developed in the Northern Territory, South Australia, and eastern Australia.
• For the southern cool season (April to October), rainfall averaged across southern Australia (south of 26°S) was 33% below the 1961–1990 average, with severe deficiencies extending inland along mainland western and eastern coasts.
• Longer term rainfall deficiencies, on the 6- and 11-month periods, exist in all states and Territories.
• October soil moisture was below average (in the lowest 30% of all years since 1911) for much of Australia, particularly in the south and east.
• Low streamflows were observed mostly at sites in eastern New South Wales, south and south-east Queensland, south-west of Western Australia, most sites in South Australia, west of Victoria and Tasmania.
• Storage levels remain low in some parts of southern and central Queensland, eastern parts of New South Wales, central Tasmania, and urban areas of Perth.
• For November 2023 to January 2024, below median rainfall is likely to very likely (60% to greater than 80% chance) for northern, western, central and southern Australia.

Streamflows high in parts of the northern Australia and eastern Victoria; low in south eastern Australia and in the west of Western Australia

Areas of average to below average rainfall and soil moisture, and subsequent low streamflow conditions, were largely concentrated in the south-west of Western Australia, and south-west of southern and south-eastern Australia. Streamflow was average at 42% of the 623 sites across the country (based on records since 1975). Below to very much below average streamflow was observed at 39% of the 623 sites, mostly associated with below average rainfall and drier catchment conditions, particularly in the eastern New South Wales, south and south-eastern Queensland, south-west of Western Australia, most sites in South Australia, west of Victoria and Tasmania.

In October, above to very much above average streamflow was observed at 19% of sites, mainly in eastern Victoria and northern Australia, including the Kimberley (Western Australia), Northern Territory and north-east of Queensland's wet tropics. In eastern Victoria, moderate to major flood warnings were issued for numerous rivers in early October and downstream movement of floodwater resulted in higher-than-average streamflow for the month.

Overall high storage levels across the country, but low storage levels at several locations

October had below to very much below average rainfall and soil moisture, particularly for south-eastern quarter of Queensland; large parts of South Australia and particularly in the south-west of Western Australia, west of Victoria and north of New South Wales, resulting in a slight decrease in some storage levels from September. By the end of October, the total water storage level in Australia (across Australia's 306 public storages) was at 77.1% of capacity, slightly lower than the previous month, but higher than at the same time last year. Despite most of Australia's major storages being high, storage volumes remain low in several locations, particularly in south and central Queensland, eastern parts of New South Wales, central Tasmania, and urban areas of Perth.

Due to below average rainfall and dry catchment conditions in the northern Murray–Darling Basin, combined storages were 90.8% full at the end of October, a slight decrease, by 1.0%, from September. The combined Basin storages are 9.0% lower since the same time last year, when they were affected by record rainfall and widespread riverine flooding.

Due to very much below average rainfall and dry catchment conditions in October for most of south-west Western Australia, there was a slight decrease in some storage levels. Perth's surface water storages remained low (51.8% full) at the end of October, a 2.0% increase from September, and a 8.0% decrease from the same time last year (59.8%). Long-term declines in surface water inflows to Perth's storages means the city's water supply is generally more reliant on desalination and groundwater sources.

Serious to severe rainfall deficiencies since May, and dry catchment conditions across large parts of south-eastern Australia, including most of south-eastern Queensland, resulted in decreased volumes for many storages (decreased volumes for 64 storages in the North East Coast drainage division) from last month. Water levels in the Nogoa Mackenzie system in central Queensland remain low, below half capacity (31.7% full) at the end of October, a 3.3% decrease from September and a 7.3% decrease from the same time last year (39.0%). Water storage in Wivenhoe was slightly decreased to 64.6% full by the end of October, a decrease from same time last year (79.4%). In central Queensland, water storage in Fairbairn was below half capacity at the end of October, at 31.3%, a 3.2% decrease from September, and it was a 6.7% decrease from same time last year (38.0%).