Australia in April 2023

In brief

• April rainfall was 35.7% above average for Australia as a whole, the highest since 2006.
• Rainfall was above average for most of Western Australia, Northern Territory and South Australia, much of Queensland's south-west and Cape York Peninsula, parts of southern New South Wales and most of central and western Victoria.
• Rainfall was below average for scattered areas in south-eastern Queensland and northern coastal New South Wales, parts of Western Australia's Gascoyne and Central West, and south-western Tasmania.
• Australia's national area-average mean temperature was just 0.01 °C above the 1961–1990 average for April, the lowest since 2015.
• The national area-average mean maximum temperature for April was 0.05 °C below average and the mean minimum temperature was 0.08 °C above average.
• Mean maximum temperatures were above average for parts of north-eastern Northern Territory and most of northern and eastern Queensland and Tasmania. Mean maxima were below average for much of Western Australia and parts of western Northern Territory, eastern New South Wales and western Victoria.
• Mean minimum temperatures were above average for most of the northern tropics, western South Australia, Victoria and Tasmania, and below average in western Western Australia and parts of New South Wales and Queensland.

Further discussion and tables of records for each state and the Northern Territory can be found in the individual regional climate summaries, published on 3 May 2023.

Temperatures

Nationally, it was the coolest April since 2015 with an area-average mean temperature just 0.01 °C above the 1961–1990 average for April.

The national mean maximum temperature for April was 0.05 °C below average, the coolest since 2015. The national mean minimum temperature was 0.08 °C above average.

Mean maximum temperatures were above average for parts of north-eastern Northern Territory and most of northern and eastern Queensland and Tasmania. The area-averaged maximum temperature was more than 1 °C above average for Queensland as a whole. Large parts of the north-east Queensland had mean maximum temperatures in the highest 10% of historical observations (compared with all Aprils since 1910). Many sites along the north-eastern coast of Queensland had their highest mean maximum temperatures on record for April.

Warm to hot conditions developed over north-eastern Queensland between the 8th and 16th and many stations had their highest recorded April daily temperature during this period.

Mean maximum temperatures were below average for much of Western Australia, and parts of western Northern Territory, eastern New South Wales and western Victoria. The mean maximum temperature was in the lowest 10% of historical observations (compared with all Aprils since 1910) for large parts of Western Australia.

Mean minimum temperatures were above average for most of the northern tropics extending along parts of Queensland's east coast, most of northern and western South Australia extending into neighbouring states, central and southern Victoria and all of Tasmania.

Mean minimum temperatures were below average for South West Land Division, Gascoyne and part of Goldfields in Western Australia, areas of north-west and south-east Queensland and adjacent parts of northern New South Wales. The mean minimum temperature was in the lowest 10% of historical observations (compared with all Aprils since 1910) for large parts of Western Australia. For Western Australia as a whole, the April mean minimum temperature was the lowest since 2006. Some Western Australia sites had their record lowest April mean minimum temperature or their lowest for at least 20 years.

Rank ranges from 1 (lowest) to 114 (highest). A rank marked with ’=‘ indicates the value is tied for that rank. Anomaly is the departure from the long-term (1961–1990) average.

Rainfall

April rainfall was 35.7% above average for Australia as a whole, the highest since 2006.

Rainfall was above average for most of Western Australia, Northern Territory and South Australia, much of Queensland's south-west and Cape York Peninsula, large parts of New South Wales and most of central and western Victoria.

For Western Australia, the area-averaged April rainfall was the 9th highest on record and the highest since 2000. For Northern Territory and South Australia, the area-averaged April rainfall was the highest since 2011 and 2014 respectively.

Many stations in Western Australia and some stations in South Australia and Northern Territory had their highest April total rainfall on record or their highest for at least 20 years.

Rainfall was below average for areas in south-eastern Queensland and northern coastal New South Wales, parts of Western Australia's Gascoyne and Central West and south-western Tasmania.

Significant weather and records

Tropical moisture brings showers and storms to Western Australia

Showers, thunderstorms and rain that impacted parts of Western Australia at the end of March continued into early April, as tropical moisture from a Severe Tropical Cyclone Herman, offshore from the Pilbara, streamed across the west coast. Four-day rainfall totals to 9am on the 4th of more than 30 mm were recorded at sites in Gascoyne, Interior and Central Wheat Belt districts. These regions are typically drier at this time of the year, with average April totals generally between 10 and 25 mm. In the following three days, tropical moisture combined with an upper low pressure trough bringing showers and thunderstorms to much of central and northern Western Australia.

Several sites with more than 50 years of data had their record highest daily rainfall for April.

Widespread rainfall in the south-east Australia

Between the 6th and 9th, a low pressure system developed and moved eastward across the Great Australian Bight, with low pressure troughs and cold fronts extending across south-eastern Australia. Associated cloud brought thunderstorms, showers and widespread rainfall to south-eastern South Australia, most of Victoria and Tasmania, and parts of New South Wales and Queensland. A low pressure trough triggered severe thunderstorms which brought large hail to some areas in south-western Queensland and New South Wales on the 7th. Some locations, most notably in northern Tasmania and south-western Queensland, had their record highest April daily rainfall to 9am on the 7th and 8th.

A secondary cold front crossed the south-east of the country on the 8th, bringing cold polar air in its wake, daily maximum temperatures down to 10 °C below April average and snow to the elevated areas of Tasmania, Victoria, New South Wales and the Australian Capital Territory.

Tropical Cyclone Ilsa

A tropical low that moved from the eastern Timor Sea towards the Kimberley coast reached tropical cyclone strength on the 11th and was named Tropical Cyclone Ilsa. It moved south-west, parallel to the Kimberley coast, and intensified rapidly as it tracked over warm open waters, reaching severe intensity (Category 3) on the 12th. On the 13th, the system started to move to the south, then to the south-east, towards the coast. Severe thunderstorms with heavy to locally intense rainfall and damaging to locally destructive winds affected the Kimberly from the 11th. The northern Kimberley and north-western Northern Territory received widespread falls of 20 to 50 mm to 9 am on the 13th, with isolated higher falls.

As the system approached the Pilbara coast, the automatic weather station at Bedout Island observed a 10 minute mean wind speed of 218 km/h, with a maximum (3 second) wind gust of 289 km/h. These are respectively the highest sustained wind speed and gust ever recorded by the Bureau observation network. A minimum mean sea-level pressure reading of 931.2 hPa was also recorded at Bedout Island.

Tropical Cyclone Ilsa made a landfall around midnight local time on the 14th between De Gray and Pardoo Roadhouse (Pilbara Coast) as a Category 5 system, causing extensive damage in the area. Ilsa was the first tropical cyclone to make landfall as a Category 5 system in Australia since Marcia in February 2015, and the first on the Pilbara coast since Laurence in December 2009.

After landfall, the system started to weaken as it moved south-eastwards through Western Australia with wind gusts to an extimated 180 km/h and daily rainfall totals that exceeded 100 mm at some locations. It was downgraded to a tropical low later on the 14th. Ex-Tropical Cyclone Ilsa moved across much of the southern Northern Territory on the 15th, bringing daily rainfall totals between 30 and 50 mm to southern Northern Territory and northern South Australia.

Cold and wet over southern Australia

Between the 13th and 16th, a deep low pressure system south of the Great Australian Bight extended a cold front that moved eastwards across southern Australia, while a low pressure trough that stretched across Western Australia brought moisture from ex-Tropical Cyclone Ilsa. Widespread heavy rain, strong winds and thunderstorms affected southern and inland Western Australia, southern Northern Territory and South Australia, extending through Victoria, Tasmania and New South Wales. Several long record stations in Western Australia and South Australia had their highest daily rainfall for April to 9am on the 14th and 15th, while large parts of Victoria, Tasmania and New South Wales received 20 to 40 mm to 9am on the 16th.

The cold front brought maximum temperatures 5 to 10 degrees below April average to most of southern Australia extending into western and inland Queensland, and snow to alpine areas of Victoria and New South Wales.

Coastal low in the Tasman Sea

At the end of the month, a significant cold front crossed New South Wales, bringing showers and much cooler conditions. On the 29th a coastal low formed just of the South Coast, bringing moderate to locally heavy rainfall. Daily rainfall totals, to 9am on the 30th, of 50 to 70 mm were recorded in the Southern Tablelands, and 70 to 100 mm was recorded along the South Coast before the system moved offshore. The heaviest rainfall was at Jervis Bay, where the Point Perpendicular AWS recorded 207.2 mm, an April record for the location with the composite record starting in 1899.

Rank ranges from 1 (lowest) to 124 (highest). A rank marked with ’=‘ indicates the value is tied for that rank. Departure from mean is relative to the long-term (1961–1990) average.