Issued — Monthly Summary for Australia — Product Code IDCKGC1AR0
Australia in September 2023
In brief
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Australia's driest September on record, aided by a persistent positive anomaly of mean sea level pressure that resulted in cloud-free conditions for most of the country. September was also one of the driest months overall since observations began in 1900.
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Australian September total rainfall was 70.8% below the 1961–1990 average for September.
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Rainfall in September was below average for most of southern two thirds of the country.
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Rainfall was above average only for parts of eastern Cape York Peninsula (Queensland) and the far north-east corner of the Top End (Northern Territory).
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Australia's national area-average mean temperature was 2.43 °C warmer than the 1961–1990 average, the third-warmest on record (since 1910) for September.
- This was the warmest September on record for Western Australia, and the second-warmest September on record for New South Wales, Victoria and South Australia.
- Area-average mean maximum temperature for September was 3.38 °C above average nationally, the second-warmest on record. The national mean minimum temperature was 1.48 °C above average, the eight-warmest on record.
- Mean maximum temperatures for September were warmer than average for most of Australia and over 4 °C above average for large parts in the south of the mainland.
- Mean minimum temperatures were warmer than average for most of Western Australia, South Australia and Tasmania, for southern parts of Victoria, Queensland and the Northern Territory, and for much of northern New South Wales. Mean minimum temperatures were cooler than average for a large area of the southern New South Wales and for areas scattered across northern Australia.
Further information and tables of records for each state and the Northern Territory can be found in the individual regional climate summaries, published on 4 October 2023.
Temperatures
The national mean temperature was 2.43 °C above average for September, the third-warmest on record since national observations began in 1910.
For Western Australia this was the warmest August on record. With the exception of the Northern Territory, all other states were in the top ten warmest Septembers on record.
Australia's area-averaged September mean maximum temperature was 3.38 °C warmer than average, the second warmest on record for September. Mean maximum temperatures were warmer or much warmer than average for most of Australia. Daytime temperatures were amongst the highest 10% of historical observations (compared with all Septembers since 1910) for South Australia, New South Wales, Victoria, Tasmania, Western Australia excluding the north-eastern part, southern two-thirds of Queensland and large parts in the south and some pockets scattered across the north of the Northern territory. Mean maximum temperatures were the highest on record for most of the southern half of Western Australia, most of Victoria, large parts of central and southern New South Wales and southern South Australia, and for parts of north-eastern Tasmania. Many stations had their record highest September mean maximum temperature.
New South Wales, Victoria and Western Australia had their warmest September days on record, with statewide mean maximum temperatures 5.07 °C, 3.77 °C and 3.54 °C above the 1961–1990 average respectively. For South Australia and Tasmania this September was the second-warmest on record, while for Queensland mean maximum temperature was the seventh-warmest on record.
The national mean minimum temperature was 1.48 °C above the 1961–1990 September average, the eighth-warmest on record since national observations began in 1910. Mean minimum temperatures were warmer or much warmer than average for Western Australia away from the north, most of South Australia and Tasmania, southern parts of Victoria, Queensland and the Northern Territory, and for much of northern New South Wales. Mean minimum temperatures were amongst the highest 10% of historical observations (compared with all Septembers since 1910) for much of Western Australia, large parts of South Australia extending into south-western Queensland, southern and eastern Victoria, parts of northern Tasmania and pockets of northern New South Wales. Mean minimum temperatures were the highest on record for much of the southern half of Western Australia. Many stations had their highest mean minimum temperature for September on record.
Western Australia had its warmest September nights on record, with a statewide mean minimum temperature 2.33 °C above the 1961-1990 average. For South Australia, mean minimum temperature was the seventh-warmest on record.
Mean minimum temperatures were cooler than average for a large area of the southern New South Wales and for areas scattered across northern Australia.
Areal average temperatures | |||||||||
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Maximum Temperature | Minimum Temperature | Mean Temperature | |||||||
Rank (of 114) |
Anomaly (°C) |
Comment | Rank (of 114) |
Anomaly (°C) |
Comment | Rank (of 114) |
Anomaly (°C) |
Comment | |
Australia | 113 | +3.38 | 2nd highest (record +3.45 °C in 2013) | 107 | +1.48 | 8th highest | 112 | +2.43 | 3rd highest (record +2.86 °C in 2013) |
Queensland | 108 | +2.54 | 7th highest | = 95 | +1.39 | 107 | +1.96 | 8th highest | |
New South Wales | 114 | +5.07 | highest (was +4.73 °C in 2013) | 95 | +1.14 | 113 | +3.11 | 2nd highest (record +3.51 °C in 2013) | |
Victoria | 114 | +3.77 | highest (was +2.78 °C in 1944) | 95 | +0.63 | 113 | +2.20 | 2nd highest (record +2.51 °C in 2013) | |
Tasmania | 113 | +2.02 | 2nd highest (record +2.19 °C in 2001) | = 93 | +0.56 | 110 | +1.29 | 5th highest | |
South Australia | 113 | +4.76 | 2nd highest (record +5.56 °C in 2013) | 108 | +1.72 | 7th highest | 113 | +3.24 | 2nd highest (record +4.38 °C in 2013) |
Western Australia | 114 | +3.54 | highest (was +2.79 °C in 2019) | 114 | +2.33 | highest (was +1.97 °C in 2020) | 114 | +2.94 | highest (was +2.37 °C in 2020) |
Northern Territory | 100 | +2.08 | 64 | +0.22 | 88 | +1.15 |
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
September was exceptionally dry month for Australia; nationally, it was the driest September on record (since observations began in 1900). The month was dominated by high pressure systems which brought settled weather conditions and cloudless sky for most of the country. September was also one of the driest months overall since 1900.
For Australia as a whole, rainfall was 70.8% below average for September.
September rainfall was below or very much below average for most of Australia. It was in the lowest 10% of historical observations for September (compared with all Septembers since 1900) for most of Victoria and New South Wales and large parts of north-eastern Tasmania, south-eastern Queensland and south-eastern, south-central and north-western South Australia extending to the adjacent parts of Western Australia. September rainfall was the lowest on record for coastal parts of Victoria's Central district and South West Slopes district in New South Wales.
For Victoria, it was the driest September on record since observations began, with state-wide rainfall 67.1% below average. For New South Wales as a whole, September was the second-driest on record, 82.6% below average, while for South Australia it was the seventh-driest September on record.
Only small areas of Australia received above average rainfall for the month - parts of eastern Cape York Peninsula (Queensland) and the far north-east corner of the Top End (Northern Territory).
Significant weather and records
Wet and windy in south-eastern Australia
A strong cold front and a low pressure trough crossed southern and south-eastern Australia on the 7th and 8th, with showers, thunderstorms and damaging winds for South Australia, Victoria, Tasmania, New South Wales and southern Queensland. The polar air that followed in its wake brought winter-like temperatures and low-level snow. Strong winds brought down trees, powerlines, caused significant property damage and left tens of thousands of people without power. Peak wind -gusts of 100 to 125 km were recorded across coastal and elevated parts of Victoria and New South Wales, with strongest gusts of 142 km/h and 137 km/h recorded at Thredbo (New South Wales) and. Mount Hotham (Victoria) respectively. Alpine areas in New South Wales reported 10 to 15 cm of snow, while snow flurries were reported around Oberon (New South Wales) but melted before reaching the ground. Snow was also reported at low levels in areas of Victoria and Tasmania. A strong south-westerly airflow behind the front resulted in huge waves at the south-eastern coast of South Australia and Victoria's south-west coast, with swells of more than nine meters reported at Port Fairy (Victoria).
Elevated fire danger for much of western and Northern Australia
Warm conditions under a slow-moving high pressure system resulted in high to extreme fire danger across much of northern and western Australia during most of September. In the Northern Territory, there were about 30 fires burning between the 7th and 16th September, with Barkly Fire being the biggest. Dry, fresh and gusty south-easterly winds combined with high grass fuel loads resulted in Extreme fire danger, and warnings were issued for Darwin and Adelaide River, Gregory and Barkly North fire weather districts. The Barkly Fire burnt over 10,000 km2 and resulted in closure of the Barkly Highway, while a big fire to the east of Tennant Creek posed a risk to the town between the 9th and 16th.
Severe weather in south-western Western Australia
A strong cold front moved over southern Western Australia on the 13th and 14th with damaging to locally destructive winds, widespread rain, showers and severe thunderstorms. In the 24 hours to 9am on the 13th some sites in the Busselton region recorded daily rainfall totals of 30 to 60 mm, with the highest total of 91.4 mm being recorded at Busselton Aero. Wind gusts exceeded 80 km/h at many locations and widespread damage was reported across Perth and the South-West. Some stations had their record highest September daily rainfall total to 9am on the 13th and 14th.
Very warm across southern Australia
Between 11 and 20 September, unusually warm conditions developed across southern Australia, and particularly in the south-east. Warm conditions initially developed over south-western Western Australia in a northerly airstream and moved eastwards pushed by the approaching cold front. On the 14th, many sites in elevated and alpine areas of Tasmania, Victoria and southern New South Wales had their record highest maximum temperature for September, while from the 15th to 20th, very warm to hot conditions persisted over New South Wales and far eastern Victoria. The heat peeked on the 19th with anomalies 10 to 15 °C above the September average. From the 17th until 20th, a low intensity-to-severe heat warning has been issued for the South Coast district of New South Wales, along with Greater Sydney's first Total Fire Ban since November 2020. Many stations had their highest daily maximum and minimum temperature for September on record. In addition, a number of stations, including Melbourne (Olympic Park), Sydney (Observatory Hill) and Canberra Airport, set September records for the number of consecutive days above threshold temperature. Sydney (Observatory Hill) equalled its warmest September on record with 34.6 °C on the 19th (previous instance was on 26 September 1965).
Hot and dry weather with strong northerly winds resulted in extreme fire danger warnings for Greater Sydney and the Hunter region on several days and Catastrophic fire danger warning for the New South Wales' Far South Coast on the 19th. More than 70 grassfires and bushfires were burning across eastern New South Wales and south-eastern Queensland during this period.
From the 26th to the end of the month, another period with warm to hot conditions affected southern parts of the country, and particularly southern Western Australia and South Australia and many stations had their highest daily maximum and minimum temperatures for September on record. Geraldton Airport (Western Australia) recorded 39.0 °C on the 27th, a highest daily maximum temperature for September for a location with a composite record 117 years long.
Area-average rainfall | ||||
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Rank (of 124) |
Average (mm) |
Departure from mean |
Comment | |
Australia | 1 | 4.8 | −71% | lowest |
Queensland | 17 | 2.8 | −78% | |
New South Wales | 2 | 6.1 | −83% | 2nd lowest (record 5.2 mm in 2017) |
Victoria | 1 | 21.2 | −67% | lowest |
Tasmania | 19 | 87.3 | −35% | |
South Australia | 7 | 3.4 | −81% | 7th lowest |
Western Australia | 20 | 5.1 | −50% | |
Northern Territory | = 7 | 0.4 | −95% | equal 7th lowest |
Murray-Darling Basin | 1 | 5.6 | −84% | lowest |
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.
Hottest day | 42.8°C | Mandora (WA) on the 28th |
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Coldest day | -1.6°C | Falls Creek (Vic.) on the 8th |
Coldest night | -7.5°C | Perisher Valley AWS (NSW) on the 22nd |
Warmest night | 28.5°C | Bidyadanga (WA) on the 28th |
Wettest day | 91.4 mm | Busselton Aero (WA) on the 13th |
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