Australia in September 2018

In brief

  • Australia's driest September on record
  • Rainfall very much below average nationally, and particularly low across the southern mainland
  • Overall, mean temperatures above average
  • Mean maxima warmer than average for September, particularly in the tropics
  • Mean minima close to average overall, but very much cooler than average for much of Victoria, South Australia, and southern New South Wales

Temperatures

The national monthly mean temperature for September was 0.64 °C above average. For Australia as a whole, mean maxima were 1.41 °C warmer than average for the month, while mean minima were close to average at 0.13 °C below the long-term average.

Maximum temperatures were above average for much of Australia, encompassing eastern Tasmania, northern and eastern Victoria, much of New South Wales away from the coastal strip and the northwest, the majority of Queensland, the northern half of the Northern Territory, and the most of Western Australia excluding some parts of the southwest. Days were in the warmest 10% of historical observations (decile 10) for most of the Kimberley and the Top End, areas to the south of the Gulf of Carpentaria, areas along the east coast of Queensland, and an area of the coastal southeast of Western Australia.

Minimum temperatures were very much cooler than average for most of the mainland southeast, extending into Central Australia, and also cooler than average for much of the South West Land Division and South Coastal District in Western Australia. Mean minima were the lowest on record for September for a large area extending along the Murray River from around Albury, across northwestern Victoria, extreme southwestern New South Wales, and the Murraylands, Riverland, and Flinders regions of South Australia, reaching to west of Port Augusta. Numerous stations in Victoria and South Australia observed their coolest mean minima for September, with a handful of stations in southern New South Wales also setting records. Records for lowest daily minima were less common, but were observed at some stations in southwest Western Australia on the 15th and 16th.

The mainland southeast experienced a particularly cool period around mid-month, with nights below zero across large parts of the grain-growing regions of southwest Western Australia, Victoria, and South Australia. Frost damage has led to crops being cut for hay in a number of areas in northern Victoria and eastern South Australia.

Conversely, some areas did observe warmer than average minima for the month, including the coastal Pilbara in Western Australia, the southwest Top End in the Northern Territory, and a large area spanning northeastern New South Wales and southeastern Queensland.


Areal average temperatures
Maximum Temperature Minimum Temperature Mean Temperature
Rank
(of 109)
Anomaly
(°C)
Comment Rank
(of 109)
Anomaly
(°C)
Comment Rank
(of 109)
Anomaly
(°C)
Comment
Australia 93 +1.41 55 −0.13 79 +0.64
Queensland 96 +1.50 61 +0.14 =81 +0.82
New South Wales 90 +1.74 = 56 +0.11 81 +0.93
Victoria 75 +0.92 = 19 −0.96 51 −0.01
Tasmania 78 +0.49 60 +0.10 =71 +0.30
South Australia 66 +0.75 13 −1.05 = 37 −0.14
Western Australia 99 +1.60 54 −0.04 89 +0.78
Northern Territory 85 +1.38 58 +0.03 73 +0.71

Rank ranges from 1 (lowest) to 109 (highest). A rank marked with ’=‘ indicates the value is tied for that rank. Anomaly is the departure from the long-term (1961–1990) average.


Temperature maps
MeanAnomalyDeciles
Mean
daily
maximum
temperatures
Map of mean daily maximum temperature Map of mean daily maximum temperature anomalies Map of mean daily maximum temperature deciles
Mean
daily
minimum
temperatures
Map of mean daily minimum temperature Map of mean daily minimum temperature anomalies Map of mean daily minimum temperature deciles
Mean
daily
temperatures
Map of mean daily temperature Map of mean daily temperature anomalies Map of mean daily temperature deciles

Rainfall

September was an exceptionally dry month, especially across the southern mainland. Rainfall was the lowest on record for September both nationally, and for southern Australia (i.e. those areas south of 26°S). It was the second driest September on record for Victoria, third driest for Western Australia, and fourth driest for South Australia.

Rainfall totals were in the lowest 10% of historical rainfall totals for the month in large areas including greater southwestern Western Australia (southwest of a line between about Geraldton and Esperance), South Australia from Ceduna east across the Eyre Peninsula and agricultural districts, much of the western half of New South Wales, and nearly all of Victoria except parts of South and West Gippsland. September rainfall was below average across most of the remainder of southern Australia, Queensland and the Northern Territory, but near average for large parts of northeastern New South Wales and large areas of southeastern to Central Coast Queensland.

Total rainfall for the month was the lowest on record for September at many sites in Victoria and Western Australia, and a handful of locations in New South Wales and Tasmania.

The year to date has also been exceptionally dry over the mainland southeast, with significant rainfall deficiencies continuing to affect large areas of eastern Australia at timescales out to around two years duration.

Above average rainfall was only recorded in small pockets, including northeastern New South Wales, parts of the coastal Kimberley, and about Joseph Bonaparte Gulf with very much above average rainfall in part of the southwestern Top End due to unseasonable rainfall in the last week of the month.


Area-average rainfall
Rank
(of 119)
Average
(mm)
Departure
from mean
Comment
Australia 1 5.2 −69% lowest
Queensland 15 2.7 −79%
New South Wales 21 15.9 −54%
Victoria 2 22.5 −66% 2nd lowest (record 22.0 mm in 1914)
Tasmania 15 87.0 −37%
South Australia 4 2.9 −83% 4th lowest (record 2.3 mm in 1938)
Western Australia 3 2.7 −75% 3rd lowest (record 1.6 mm in 1939)
Northern Territory 39 1.1 −85%
Murray-Darling Basin 6 10.2 −70% 6th lowest

Rank ranges from 1 (lowest) to 119 (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.


Rainfall maps
TotalsPercentagesDeciles
Total
rainfall
Map of total rainfall Map of percentage of normal rain Map of rainfall deciles


Australian weather extremes during September 2018
Hottest day 40.9 °C    at Roebourne Aero (WA) on the 26th
Coldest day −2.7 °C    at Mount Hotham (Vic.) on the 2nd
Coldest night −9.7 °C    at Thredbo AWS (NSW) on the 24th
Warmest night 27.3 °C    at Bradshaw (NT) on the 25th
Wettest day 100.0 mm at Ballina Airport AWS (NSW) on the 5th


Notes

The Monthly Climate Summary is prepared to list the main features of the weather in Australia using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

Climate Summaries are usually published on the first working day of each month.

This statement has been prepared based on information available at 12 noon EST on Monday 1 October 2018. Some checks have been made on the data, but it is possible that results will change as new information becomes available, especially for rainfall where much more data becomes available as returns are received from volunteers.

Long-term averages in this statement and associated tables are for the period 1961 to 1990 unless otherwise specified.

The system used for calculating areal averages of rainfall was changed in May 2009; the main effect was that current and historical values for Tasmania were increased. Since December 2012, ACORN-SAT has been used for calculating areal averages of temperature; the major change from earlier datasets is that the ACORN-SAT dataset commences in 1910, and hence rankings are calculated using a larger set of years.


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