- Averaged across Australia north of 26°S, the wet season (October 2022 to April 2023) rainfall was 690.4 mm, the sixth-wettest season on record (since 1900–01) meaning the top six wettest seasons have all occurred during La Niña years.
- There were 6 tropical cyclones in the Australia region from October 2022 to April 2023, with a seventh forming pre-season in July 2022; this compares to an average of 11 for all years since 1969–1970, or 9 since 2000–2001.
- Rainfall was well above average for most northern areas with small pockets recording their highest wet season rainfall on record.
- Wet season rainfall was below average for areas of the northern coast of the Gascoyne in Western Australia; and areas in the Central Coast, and a strip from the Wide Bay and Burnett to the Central Highlands districts in Queensland.
- The mean maximum temperature for northern Australia's wet season was 0.25 °C below the 1961–1990 average, the lowest since 2011–12, while the mean minimum temperature was 0.31 °C above the 1961–1990 average.
- Mean minimum temperatures were in the top 10% of the historical record (since 1910–11) for large parts of the far north.
- La Niña conditions in the tropical Pacific Ocean were in place at the start of Northern Australia wet season and remained active for the majority of the season until the Bureau declared an end, moving to an El Niño WATCH in March 2023.
- The Indian Ocean Dipole (IOD) was in a negative phase at the start of the wet season returning to a neutral phase by early December 2022.
- Warmer than average waters surrounding northern Australia during parts of the season have likely contributed to most of Northern Australia receiving very much above average rainfall, including some areas receiving highest on record rainfall totals.
- The wet conditions resulted in many rivers in the north running full, including the Fitzroy River in the Kimberley, and contributed to increased inflow to the storages. Lake Argyle and Darwin River storages in February, and a number of storages in Queensland, including Burdekin Falls had water levels above their full capacities through to the end of the period.
- Multiple floods occurred in major rivers in the north, affecting widespread areas and communities in Queensland, Western Australia and the Northern Territory.
The total area-average rainfall for northern Australia over the 2022–23 wet season (October 2022 to April 2023) was 690.4 mm, which was 45% above the 1961–1990 average of 476.4 mm. This makes the 2022–23 wet season the sixth-wettest on record (compared to all years since 1900–01).
Rainfall was above average for most of the region, and very much above average (in the highest 10% of historical observations) for the region extending from the West Kimberley Coast of Western Australia to over central and north-west Northern Territory and north-west Queensland and Cape York Peninsula (Figure 1). Highest on record rainfall for the season was recorded in small northern parts of Cape York Peninsula as well as in small pockets of central Northern Territory and the Kimberley region of Western Australia.
Below average rainfall (in the driest 30% of all wet seasons since 1900–01) was recorded in the Central Coast, and an area of the Wide Bay and Burnett to Central Highlands districts in Queensland; and for a pocket of the northern Gascoyne coast in Western Australia.
As is typical of La Niña periods, much of Northern Australia saw an earlier than average northern rainfall onset date (the date when rainfall accumulated since 1 September reached 50 mm), with large parts of the region having an onset date at least 4 weeks earlier than the 1981–2010 median (Figure 2). This was evident in the Kimberley region, parts of the Gascoyne region extending to the southern interior of Western Australia, over areas of the north-east, interior and south of the Northern Territory, and areas of Queensland's south-west region across to the Central Coast and northern parts of the Cape York Peninsula.
Small pockets of the Pilbara coast in Western Australia, the interior of the Northern Territory, and the Gulf Country and northern coastal areas of Queensland experienced a later northern rainfall onset date, where onset dates were at least 3 weeks later than the 1981–2010 median.
For most areas, there was a significantly wetter than average start to the wet season for Northern Australia. For Northern Australia, October 2022 was the eight-wettest October on record (since 1900) and the wettest October since 2010, while November 2022 was the fifth-wettest November on record and the wettest November since 2000. For both of these months, large parts of the region recorded total rainfall in the top 10% of records (since 1900) with parts of northern Western Australia extending into western Northern Territory observing their highest November rainfall on record.
The above average rainfall continued over the season with only March 2023 recording area-averaged rainfall below the 1961–1990 average. The first active monsoon period occurred late in December 2022, with an official monsoon onset date at Darwin of 22 December 2022, which was close to the average date of 29 December (the average over all years since 1957).
January 2023 rainfall was again well above average, being the ninth-wettest January on record (all years since 1900), and wettest January since 2017. Above average rainfall (rainfall in the top 10% of all years since 1900) was recorded from the West Kimberley Coast across to southern and central Northern Territory, and in the Gulf Country, Cape York Peninsula and central and coastal areas of Queensland. Parts of the Kimberley in Western Australia reported their highest January rainfall on record.
Large areas of Western Australia and western and southern parts of the Northern Territory recorded April monthly rainfall totals in the top 10% of all years since 1900. Areas inland of the Pilbara, in Western Australia observed their highest April rainfall on record.
The mean maximum temperature for northern Australia's wet season was 0.25 °C below the 1961–1990 average, the lowest since 2011–12, while the mean minimum temperature was 0.31 °C above the 1961–1990 average.
Mean maximum temperatures were below average for most of northern Australia (Figure 3), especially parts of the west coast and interior region covering Western Australia, central Northern Territory and the north-west to central region of Queensland. The Cape York Peninsula extending towards the central coast of Queensland and northern Arnhem land saw above average maximum temperatures for the wet season period.
The wetter than average conditions resulted in close to average to below average maximum temperatures for most of the season. November 2022 and January 2023 were particularly cooler than average, with area-averaged anomalies more than 1 °C below the 1961–1990 average. During November 2022, parts of the Pilbara Coast extending to central parts of Western Australia recorded their lowest November maximum temperature on record.
March 2023 saw most of the Northern region experience warmer than average maximum temperatures. A large area extending from the Gascoyne region to the Southern Interior of Western Australia, across to southern Northern Territory and Queensland, and along the eastern Queensland coast recorded above average maximum temperatures in the highest 10% of all years since 1910.
Much of the eastern Queensland coast from the northern to the southern district reported maximum temperatures above their average in April 2023. Areas along the Cooktown to Townsville coasts recorded their highest April maximum temperatures on record.
Mean minimum temperatures were warmer than average for northern and southern parts of northern Australia (Figure 4), especially across the Kimberley, northern parts of the Northern Territory, around the Gulf of Carpentaria, and Cape York Peninsula extending to the Mackay Coast. Below average minimum temperatures were recorded from the Kimberley coast to the Southern Interior of Western Australia, and across to the interior of Northern Territory, as well as in small parts of central and south-eastern Queensland. A small area of the Southern Interior of Western Australia observed minimum temperatures in the lowest 10% of all years since 1910.
As a region, the minimum temperature anomaly was the greatest in October 2022 where the area-averaged anomaly was 1.25 °C above the 1960–1991 average. During October, northern parts of the region recorded October minimum temperatures in the highest 10% of all years since 1910 with parts of the Kimberley, areas around the Gulf of Carpentaria and parts of the Queensland coast recording their highest October minimum temperatures on record.
The area-averaged anomaly for the remaining months of the season was within 1 °C of the 1960–1991 average.
At the start of the wet season, above average rainfall and wet soil moisture conditions accelerated runoff and a number of river gauges recorded high flows in the eastern and northern parts of the region in October. This increased inflows to the surface water storages such as in Darwin River, Burdekin Falls and Julius storages.
Soils became increasingly saturated in November particularly in the western catchments. River flows were high in the majority of the northern and eastern catchments through the end of the month. Flooding occurred in some rivers in Queensland including along the Fitzroy River at Noonkanbah (south of Fitzroy Crossing), however it was not widespread across the north.
In December, Tropical Cyclone Ellie produced heavy rainfall over northern and central parts of the Northern Territory and flood watches were declared in the MacArthur and Upper Victoria rivers in the north where flows were high. However, the soils in western and eastern areas of the Northern Australia started to dry and in particular, inflows to the eastern storages dropped.
In January, due to monsoon bursts and Tropical Cyclone Ellie, wet conditions prevailed in the southern half of the Northern Territory especially across the south and west Kimberley, but in and around Darwin remained dry. Major flood warnings were announced for West Kimberley District, Fitzroy River and some communities in the Fitzroy catchment were isolated. Flooding also occurred in northern and central Queensland that isolated communities in western, north-western and far northern Queensland including Doomadgee, Burketown, Urandangi, Normanton and Karumba.
Most of the northern NT experienced wet conditions in February except for the south-west. Many sites recorded high flow rates along the Daly, Katherine and Waterhouse rivers in the north, and combined with the very wet conditions particularly in northern NT and the western Queensland border with NT, runoff and inflow to the storages was considerable. This resulted in the majority of the storages including Lake Argyle, Darwin River and Burdekin Falls filling to more than 100% capacity. Flood Warnings continued in northern and western Queensland. Widespread disruption to transport networks and the isolation of communities occurred including in Doomadgee, Bedourie, and Karumba.
March was drier than average for parts of the Top End and the Kimberley and as soils dried out, floodwaters also started to recede in western areas. However major flooding occurred on the Georgina River between Roxborough Downs, Glenormiston and on the Lower Flinders River. A large number of storages in the east and north were above capacity during March. Northern Territory was wet in April especially in the western and far south parts.
Tropical cyclone Ilsa resulted in the wettest April on record at many sites in the north and south-west of WA. The coastal Carpentaria district remained dry. Although flows eased to near median in many rivers in eastern Queensland and northern NT, high flows continued in most rivers in north-east WA. Lake Argyle and Darwin storages were at more than 100% capacity and most eastern storages were near full. Eyre Creek reached major flood peak levels. Bedourie remained isolated and many roads were closed with flooding at both Glengyle and Bedourie slowly easing.
La Niña was declared underway by the Bureau of Meteorology in September 2022 and the event continued for the majority of the wet season for Northern Australia. La Niña conditions began weakening early in 2023 with the Bureau declaring an end to La Niña and moving to an El Niño WATCH in March 2023. The weekly NINO3 SST index in the eastern tropical Pacific was at its coolest in the week to 6 November 2022 (−0.75 °C) and the weekly NINO3.4 SST index in the central tropical Pacific was at its lowest at the beginning of the northern wet season in the week to 2 October 2022 (−0.76 °C).
La Niña typically brings above average rainfall to much of northern Australia during the wet season. The 2022–23 La Niña contributed to an early start to the wet season for almost all areas with a notable exception of the Pilbara coast in Western Australia. The 2022–23 La Niña was also conducive to most of Northern Australia receiving very much above average rainfall, including some areas receiving their highest on record rainfall totals. Including 2022-23, the six wettest October to April periods (since 1900-01) for northern Australia have all been during La Niña events.
The Southern Oscillation Index (SOI) was positive during most of the northern Australian wet season, typical of an active La Niña phase. The monthly SOI was above the La Niña threshold of +7 from the start of the season to February 2023 with the exception of November 2022 where it dipped to +4.6. From around the beginning of 2023, the SOI started to decrease towards neutral values and from March onwards, the monthly SOI was close to zero.
The Indian Ocean Dipole (IOD) was in a negative phase at the start of the wet season, resulting in warmer than average sea surface temperatures in the eastern Indian Ocean. The negative IOD, and a warmer eastern Indian Ocean generally, was likely conducive to the above average rainfall observed in parts of northern Australia during October and November 2022. The IOD returned to a neutral phase by December 2022, in line with the typical life cycle of an IOD event. Above average sea surface temperatures across the eastern Indian Ocean may have contributed to cloud bands that brought rainfall to Western Australia, as well as inland parts of northern Australia.
The Madden–Julian Oscillation (MJO), which is the major climate influence for tropical Australia on weekly to monthly timescales, likely influenced tropical Australia at a few key points during the season. The MJO was in the Australian region during parts of October and November and most of December in 2022, potentially contributing to the wetter conditions across northern Australia during these months. The MJO was absent during January 2023, entering the Maritime Continent region during the first half of February and reaching its peak strength and activity for the 2022–23 Australian wet season. The MJO was almost completely absent from the Australian region during March, with strong MJO activity in or near the western Pacific Ocean. When the MJO activity is closer to South America than Australia, there is often reduced cloudiness over northern Australia, with reduced convection and rainfall. The MJO entered the Australian region again in the first half of April.
The peak of local MJO activity in December likely contributed to the start of the first active monsoon over northern Australia on 22 December 2022. There were only a few other main active events of the Australian monsoon affecting the Australian continent during the northern wet season, occurring around mid-January into mid-February 2023 and late February into March 2023.
The Southern Annular Mode (SAM) was in a strong positive phase from October to mid-January 2023 with the monthly SAM index value for January being the highest on record (since 1979). The Southern Annular Mode is often positive during La Niña and during the northern wet season the persistently positive SAM was also boosted by a strong polar vortex over Antarctica. From February to April 2023, the weekly SAM index was closer to neutral values, with brief periods of positive and negative values. The SAM averaged over the northern wet season was the fourth highest since 1979–1980.
In addition to the influence of natural climate drivers, Australia's climate is increasingly influenced by global warming. Australia's climate has warmed on average by 1.47 ± 0.24 °C over the 1910–2020 period, with most of the warming occurring since 1950. Rainfall across northern Australia has increased during the northern wet season since the 1970s, with more high intensity and short duration rain events.
- For the Australian tropical cyclone region, as defined for the Tropical Cyclone Outlook, there were 6 tropical cyclones (Darian, Ellie, Freddy, Gabrielle, Herman and Ilsa) that formed during the northern wet season.
- Unnamed tropical cyclone 01U formed during July prior to the wet season, increasing the count to 7 tropical cycles for the 2022–23 year.
- The long-term average (since 1969–70) number of tropical cyclones in the Australian region is 11, while in recent decades (since 2000–01) the average is 9.
- Only two tropical cyclones (Ellie and Ilsa) made landfall on the Australian mainland with at least Category 1 strength, which is fewer than the long term average of four.
- Five tropical cyclones reached severe strength (at least Category 3) in the Australian region, with 3 systems (Darian, Herman and Ilsa) reaching Category 5 intensity, the highest rating, the first occasion since 2005–06.
- When TC Ilsa crossed the Pilbara coast of Western Australia (WA) in April, it was the first coastal crossing of a Category 5 system in Australia since 2015, and the first for WA since 2009.
- There were around 16 observed tropical lows in the Australia region during the October 2022 to April 2023 period.
Tropical Cyclone Darian
- Tropical Low 05U formed to the north of Cocos Island on 13 December and remained as a weak system until it began moving southwards on 16 December reaching tropical cyclone strength on 18 December.
- Tropical Cyclone Darian rapidly intensified to a Category 3 cyclone in 24 hours and continued to intensify, reaching Category 5 cyclone strength on 21 December, before moving in RSMC La Reunion Area of Responsibility.
- Darian was the first cyclone of the northern wet season and the first to reach Category 5 strength.
Tropical Cyclone Ellie
- Tropical Low 06U formed within the monsoon trough to the north-west of Darwin in the Timor Sea on 21 December 2022 and intensified quickly as it moved south, reaching Category 1 intensity on the evening of 22 December shortly before crossing the coast as Tropical Cyclone Ellie near Peppimenarti.
- As a tropical low, Ellie continued moving southeast across central parts of the Northern Territory where heavy rainfall led to flooding in many communities, most notably Timber Creek, and cut major roads.
- It became slow moving over the inland Kimberley and produced multiple days of heavy rainfall. The Fitzroy River reached its highest levels on record, peaking at 15.81 m on the afternoon of 4 January at Fitzroy Crossing, isolating the town and many other nearby communities and significantly damaging the Great Northern Highway bridge.
- Heavy rainfall continued to be associated with the system as it traversed the Kimberley producing weekly totals of around 400 mm to 750 mm, eventually dissipating over the southwest of the Northern Territory on 9 January.
Tropical Cyclone Freddy
- A tropical low 13U was first analysed south of Bali on 5 February 2023 and while tracking slowly south westwards away from the Australian mainland, it developed into a Category 1 system as Tropical Cyclone Freddy on 6 February 2023.
- Freddy continued to develop as it took a west-southwest track intensifying into a Category 3 (severe) system on 7 February after a period of rapid intensification. Taking a generally westward track, Freddy fluctuated between Category 2 and Category 4 intensity with peak intensity in the Australian region on 12 February.
- On 14 February Freddy moved into La Reunion's area of responsibility with minimal impacts to the Australian coast, however Freddy was an exceptionally long-lived cyclone which was named for 34 days (to be verified by the WMO) and causing significant impacts in Madagascar, Mozambique and Malawi. The current record of 31 days is held by Hurricane/Typhoon John in 1994.
Tropical Cyclone Gabrielle
- Tropical low 14U formed in the Coral Sea south of the Solomon Islands on 5 February. The low moved west-southwest and developed into a Tropical Cyclone Gabrielle on 8 February as it passed to the east of Willis Island.
- Gabrielle turned to the south and then to the southeast and on 10 February intensified into a Category 3 (severe) tropical cyclone as it moved southeast away from the Australian mainland. Gabrielle transitioned into a sub-tropical cyclone as it passed close to Norfolk Island on 11 February. The cyclone had a very large gale radius resulting in high waves causing large boulders to be flung onto the Cascade Pier damaging railings and the pier surface.
- The low subsequently moved to the south causing significant impact to the North Island of New Zealand.
Tropical low 16U
- Tropical Low 16U formed during an active burst of the monsoon trough on 22 February to the north of Broome in Western Australia. Tracking north-westerly, 16U crossed the North Kimberley coast on 27 February.
- The low continued to move east over the Kimberley and into the Northern Territory between 1 and 5 March causing widespread heavy rainfall and flooding of rivers and roads producing weekly totals of around 200 mm to 400 mm.
- The low drifted over the waters off the Gulf of Carpentaria on 5 and 6 March before moving back inland over northwest Queensland on 7 March. The slow moving low brought more heavy rainfall and flooding rains to the area at the base of the Gulf with weekly totals up to 650 mm until finally dissipating during 10 March.
- A few sites recorded their highest March or annual daily rainfall on record, including Alexandria which recorded 262.0 mm in the 24 hours to 9 am on 3 March (its highest daily rainfall across a record of 130 years) and Century Mine which recorded 313.4 mm in the 24 hours to 9 am on 8 March (its highest daily rainfall across a record of 20 years) along with an additional 220.2 mm on 9 March.
- Record breaking floods occurred across northwest Queensland with flood waters leading to evacuations and significant inundation of many rural properties and some towns.
Tropical Cyclone Herman
- A weak tropical low 21U developed to the north of Cocos Islands on 28 March and tracked to the southeast over open waters.
- The low rapidly developed and Tropical Cyclone Herman was declared on 29 March. Intensification remained rapid with Herman reaching Category 5 by 31 March.
- Herman was a small intense system both rapidly intensifying and weakening, and on 2 April Herman turned to the west as a tropical low eventually dissipating over open waters of the Indian Ocean.
Tropical Cyclone Ilsa
- A tropical low 23U formed in the Timor Sea on 6 April and whilst tracking slowly south westwards developed into a Category 1 system as Tropical Cyclone Ilsa on 11 April.
- Ilsa rapidly intensified to a Category 5 tropical cyclone before crossing the north Pilbara coast on the evening of 14 April with an estimated maximum 10-minute mean wind intensity of 220 km/h. Major buildings including several pastoral stations sustained severe damage.
- Ilsa weakened and tracked east south-eastwards inland, producing daily totals up to 100 mm along central parts for the next several days.
- The peak 219 km/h 10-minute mean wind observation at Bedout Island is the highest ever recorded in Australia and the 289 km/h wind gust was the highest wind gust ever recorded by a Bureau of Meteorology instrument.
- Ilsa was the first coastal crossing of a 5 system in Australia since 2015, and the first for WA since 2009.
- Area-average data and time series charts for the northern wet season period
- Rainfall maps for the 7-months periods ending April
- Wet season climate summary for Northern Territory
About the data
All values in this statement were compiled from data available as of 12 May 2023. Subsequent quality control and the availability of additional data may result in minor changes to final values.
The use of current and historical climate information allows for comparison of climate impacts from one year to the next and aligns with other reporting processes that occur over northern wet season periods.
This statement was prepared using the following sources:
- Rainfall maps from the Australian Gridded Climate Dataset (AGCD) analyses.
- Temperature maps from the Australia Water Availability Project (AWAP) analyses.
- Area-average time series for the northern wet season are calculated from the homogenised Australian temperature dataset (ACORN-SAT) and AGCD monthly rainfall.
- Root-zone soil moisture from Australian Water Resources Assessment Landscape model (AWRA-L) 7.0 analyses.
- Water storage information and the Murray-Darling Basin Information Portal.
- Sea surface temperature from the ERSSTv5 dataset.