Australia in September 2022

In brief

• For Australia as a whole, September rainfall was the fifth-highest on record.
• Rainfall was above or very much above average for most of Australia, although below average rainfall was observed in western Tasmania, South and West Gippsland in Victoria, and south-west Western Australia.
• For Queensland, New South Wales, and Western Australia area-averaged rainfall was amongst the ten highest on record for September compared with all Septembers since 1900.
• Australia's national area-average mean temperature was 0.69 °C above average for September.
• Area-average mean maximum temperature for September was 0.02 °C above average nationally, while the mean minimum temperature was 1.36 °C above average — the tenth-highest on record for September.
• Both mean maximum and mean minimum temperatures were above to very much above average for the northern tropics, with mean maxima warmest on record for September for some areas.

Temperatures

The national mean temperature for September was 0.69 °C warmer than the 1961–1990 average for Australia as a whole.

Area-average mean maximum temperature for September was 0.02 °C above average nationally, while the mean minimum temperature was 1.36 °C above average — the tenth-highest on record for September since national records began in 1910.

The mean maximum temperature for September was above or very much above average across the northern tropics, and warmest on record for September for much of the Top End and large parts of Cape York Peninsula. Mean maxima for September were above average for far south-west Western Australia and the north-western half of Tasmania, but were cooler than average for much of the mainland away from the tropics, and very much cooler than average for parts of the eastern states and some areas of inland Western Australia.

Mean minimum temperatures were also above to very much above average for the northern tropics, along the eastern seaboard, for much of Victoria and Tasmania, and across most of the southern half of Western Australia extending into western South Australia.

Some stations in the northern Kimberley, the north of the Northern Territory and around the coast of Cape York Peninsula had their warmest September on record (mean temperature).

Rank ranges from 1 (lowest) to 113 (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 rainfall was the fifth-highest on record for Australia as a whole, with the national area-average 103% above the 1961–1990 average (i.e. just over twice the average).

Rainfall was above or very much above average for most of Australia, and in the highest 10% of historical observations (since 1900) over large areas of New South Wales and northern Victoria, southern Queensland, and much of Western Australia from the north-west to the interior. A large number of stations in eastern New South Wales and south-eastern and southern Queensland had their wettest September on record. Records were also set across a large area of north-west Western Australia, where broad areas typically receive monthly rainfall totals of less than 5 mm during September and where monthly totals above 10 mm occurring in less than 10% of years.

Below average rainfall was observed in western Tasmania, South and West Gippsland in Victoria, and south-west Western Australia.

Significant weather and records

Unusual heavy rain in north-west Western Australia

Tropical moisture combined with weather systems including a low pressure trough to the west of Western Australia early in September, bringing several days of unusually heavy rain associated with a large band of cloud extending across Western Australia and streaming into the Northern Territory and western South Australia. Daily rainfall of 20 to 40 mm across the north-west during the 24 hours to 9am on the 3rd. This region is typically very dry at this time of the year, with average September totals of less than 5 mm. A large number of stations set September records, including several with over 100 years of observations.

Tropical moisture brings storms to South Australia and the eastern states

A large mass of cloud accompanied a cold front crossing southern Australia as a low pressure system passed across the Great Australian Bight, drawing tropical moisture in from the north. Storms resulted across parts of South Australia on the 7th, with heavy rain, hail and some flash flooding around Port Augusta, and continued across much of inland eastern Australia into the 9th as the system tracked eastwards. Rain falling onto already wet catchments saw a continuation of flooding in parts of the east, particularly across inland areas of southern Queensland and New South Wales, although minor or moderate flooding was also reported in parts of northern Tasmania and north-eastern Victoria. A few stations around the Maranoa district in Queensland set daily rainfall records for September on the 9th.

Heavy rain and thunderstorms in south-east Australia

During the middle of September, a deep low pressure system was moving slowly eastward well south of the Great Australian Bight, with a complex system of cold fronts and troughs extending across south-east Australia. Associated cloud and some embedded thunderstorms brought heavy rainfall over some areas.

Significant rain fell on the inland side of the ranges in north-eastern New South Wales and the Queensland border region exceeding some daily rainfall records for September during the 24 hours to 9am on the 16th. Renewed rises in river levels were observed in many catchments in inland New South Wales, with major flood levels reached in some rivers, with some homes flooded and many calls to the State Emergency Service to rescue people from floodwaters. Minor to moderate flooding also continued in parts of Victoria and Tasmania.

A cold front associated with the same low pressure system continued to cross the south-east over the next few days, bringing cold and showery conditions. One front on the 18th triggered a line of gusty thunderstorms across Victoria and Melbourne. Large quantities of small hail were reported in some northern and eastern suburbs, with local reports of hail just over 3 cm in diameter,  along with a tornado being reported in the western suburbs which caused damage to houses.

Offshore low exacerbates flooding in north-east New South Wales and south-east Queensland

A low pressure centre located on a trough stalled off the south-eastern Queensland coast on the 22nd. Onshore flow brought locally intense rainfall to coastal areas from the New South Wales Northern Rivers district to south-eastern Queensland, with higher totals locally in parts of the Mid North Coast and the Gold Coast, including the highest daily rainfall total for the month: 285.0 mm at Springbrook Road, near the New South Wales/Queensland border, during the 24 hours to 9am on the 23rd. The extensive rain band and thunderstorms brought multi-day totals of 25 to 50 mm to many areas across inland New South Wales and southern Queensland, resulting in rises in river levels along many already flooded rivers.

Warm in the north

The first 40 degree day of spring occurred at Wyndham Aero in Western Australia on the 12th, a few days earlier than the average for all years, but typical of La Niña  years. However, the extent of warmth across northern Australia was unusual for both maximum and minimum temperatures, with early season records set across northern Australia (i.e. the highest temperature observed so early in the season), and outright records for warmest September day at a number of stations around the Top End and the Kimberley, and records for warmest September night scattered throughout the tropics. For the Northern Territory, the days between the 21st and 27th were especially warm, following the development of a heat trough which persisted across the Top End from around mid-month until being disrupted by a southerly change and cloud mass moving in from the west late in the month. The highest temperature during the month was at Yampi Sound, near Derby in Western Australia, with 42.8 °C on the 22nd, 0.3 °C below the national September record and the highest ever observed so early in the year.

Further discussion and tables of records for each state and the Northern Territory can be found in the individual regional climate summaries, to be released on 5 October 2022.

Rank ranges from 1 (lowest) to 123 (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.