Thursday 9 January 2020 — Monthly Summary for Australia — Product Code IDCKGC1A00

Australia in December 2019

Temperatures Rainfall Extremes Important notes the top

In brief

• Warmest December on record for Australia; all States and Territories except Tasmania in the top three
• Mean maximum temperature highest on record for most of mainland Australia, except much of Victoria and parts of the coast
• Mean minimum temperature above average for nearly all of mainland Australia, and highest on record for large parts of inland Western Australia, the northwest, and interior of Australia
• December monthly (accumulated) Forest Fire Danger Index highest on record for any month
• Rainfall lowest on record for December for the country as a whole
• Amongst the five driest Decembers on record for Queensland, New South Wales, Victoria, and the Northern Territory
• Rainfall was in the lowest 10% of historical observations for much of the eastern mainland and north of the Northern Territory
• Above average rainfall confined to parts of the Pilbara and northern Gascoyne, and western Tasmania
• December concludes Australia's warmest and driest year on record

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Temperatures

It was the warmest December in 110 years of record for Australia. It was also the warmest December on record for Queensland, New South Wales, South Australia, Western Australia, and the Northern Territory. For Victoria it was the third-warmest December on record. Tasmania was the only State not to rank amongst the three warmest Decembers on record.

The national December mean temperature, 3.21 °C above average, surpassed the previous December record set in 2018 by more than a full degree. The national mean temperature anomaly for December was also the largest mean temperature anomaly for any month of the year, surpassing the previous record set in October 2015 (+3.03 °C).

Both the mean maximum and mean minimum temperatures for the month were the highest on record for December, with the national mean maximum a staggering 4.15 °C above average. This was also the largest mean maximum temperature anomaly for any month of the year, surpassing the previous record set in October 2015 (+3.60 °C).

Significant heat affected large parts of central and southern Australia from 12 December as a slow-moving high over the Great Australian Bight allowed heat to build over the continent. Temperatures in the mid to high 40s were observed across large areas, in cases for several consecutive days. As the extremely hot air mass moved eastward, large areas approached or exceeded December daily maximum temperature records across inland and southeastern South Australia, Victoria and New South Wales, southeast Queensland, Central Australia, and much of Tasmania. For a number of locations records were set for the warmest day for any time of the year.

On two consecutive days, the 17th and 18th, records were set for Australia's hottest day on record. The national area-averaged maximum temperature on the 18th was 41.9 °C, a whole degree above the value for the 17th (40.9 °C). Both of these values exceed the previous record of 40.30 °C set on 7 January 2013. In total, there were 11 days during December 2019 when the area-average maximum temperature reached at least 40 °C, and seven days which surpassed the previous record. The extreme heat during December also led to Australia's warmest week (week ending 24 December) and warmest month on record in terms of national area-averaged maximum temperature.

It is expected that a Special Climate Statement will be released covering this extreme heat event.

Maximum temperatures for December were the highest on record for most of Australia, and very much above average for most of Victoria away from the northern border; most of agricultural South Australia; for the coastal margin of New South Wales and most of east coast Queensland; some pockets of inland New South Wales and western Queensland, the central Northern Territory, inland northwestern Western Australia; and some parts of the northwest, west, and southeast coast of Western Australia. Mean maximum temperature for the month was close to average for parts of west coast Tasmania, very much above average for the northeast, and above average for the remainder of the State.

The mean minimum temperature for the month was above average to warmest on record for most of mainland Australia. December mean minima were warmest on record for the central Top End and north of the Victoria River District in the Northern Territory; the southwestern Kimberley, most of the Pilbara, Interior District, and southeast of Western Australia; across most of northern South Australia, and extending into the far northwest of New South Wales and the south of Queensland's Channel Country. Minimum temperatures for December were close to average for Tasmania and pockets of the coast in southern and far eastern Victoria, New South Wales, and tropical Queensland.

Records were numerous during the month, including many sites which set records for highest December daily temperature early in the month in the Northern Territory; across the month in Western Australia; and from the 19th to the end of the month in the Northern Territory, Queensland, New South Wales, Victoria, and South Australia; and on the 30th in Tasmania.

A large number of sites also observed record warm nights for December during the latter part of the month in the Northern Territory, Queensland, New South Wales, Victoria, and South Australia; and across the month in Western Australia.

Conversely, a cold start to the month in the southeast of Australia had seen a brief burst of record low daily maximum temperature observations between the 1st and 3rd in Victoria, New South Wales, and Tasmania.

A large number of sites in New South Wales, Queensland, the Northern Territory, South Australia, and Western Australia observed their warmest December mean maximum temperature on record, as did some sites for December mean minimum temperature in the same States.

Fire weather

The record warmth of December was accompanied by record low rainfall over eastern Australia, and followed on from very much warmer than average and drier than average conditions through most of the year.

Following particularly hazardous fire weather in spring over the eastern half of Australia, the monthly accumulated Forest Fire Danger Index (FFDI) for December was the highest on record over most of the country. For Australia as a whole, December FFDI was the highest on record for any month. The highest FFDI for individual days shows highest on record values for December (see map comparing highest daily FFDI in December 2019 against previous Decembers); in some cases the highest daily value on record for any month. On 30 and 31 December, FFDI values were highest on record for December over areas of southeastern Australia and Tasmania, including regions of significant fire activity in southern New South Wales, East Gippsland, and southeastern South Australia.

Dangerous fire weather conditions in early November had led to renewed fire activity in New South Wales and eastern Queensland, with the fires continuing to burn throughout December. Further significant fires also broke out during December in South Australia, Gippsland and northeastern Victoria, across the Alpine region, southeastern New South Wales, and Tasmania. The end of year period brought particularly challenging weather, and thousands of people in eastern Victoria and southeastern New South Wales were affected by evacuation orders as fires flared in these very dangerous conditions.

By the end of December, more than 5 million hectares had been burnt across Australia since the start of July, including 3.6 million in New South Wales, half a million in Victoria, 250 000 hectares in Queensland, and more than 60 000 hectares in South Australia. At least 18 lives had been lost, while a number of people remained unaccounted for, and more than 1600 homes had been destroyed, the bulk of which were in New South Wales. Widespread areas of heavy smoke created hazardous air quality across broad areas of eastern Australia at times during spring and continued through December, in some locations lasting for weeks at a time with little respite.

Temperature maps
	Mean	Anomaly	Deciles
Mean daily maximum temperatures
Mean daily minimum temperatures
Mean daily temperatures

Temperatures Rainfall Extremes Important notes the top

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Rainfall

December was the driest on record for Australia. Rainfall for the month was amongst the ten lowest on record out of 120 Decembers since 1900 for Queensland, New South Wales, Victoria, and the Northern Territory.

Rainfall was below to very much below average across most of Australia, and amongst the driest 10% of historical observations for the north of the Northern Territory; most of Queensland except Cape York Peninsula, the southwest, and small pockets of the east coast; most of New South Wales except the far northeast and southern inland; most of southern and eastern Victoria; northeastern Tasmania; and pockets of southern South Australia and the east of Western Australia.

Rainfall for the month was close to average for much of the western Kimberley, Pilbara, Gascoyne, and Goldfields districts in Western Australia, a small pocket on the south coast of Western Australia around Esperance, and western Tasmania. Above average rainfall was restricted to small areas, including part of western Tasmania, and areas of the Pilbara coast and northern Gascoyne in Western Australia.

The very dry December has added to ongoing serious or severe rainfall deficiencies which have affected large parts of Australia - see December Drought Statement.

A large number of sites in New South Wales and Queensland, some in the Northern Territory and Victoria, and a few in Tasmania and South Australia had their lowest December total rainfall on record.

Severe storms formed near the New South Wales border on the evening of 11 December, tracking close to Applethorpe then over Brisbane. Very heavy rainfall led to flash flooding in the metropolitan region, with the Brisbane city gauge reporting 103 mm in one hour, delivering December's average rainfall total in one night. Emergency services received 125 calls for assistance.

Severe storms also formed on the 13th over southeast Queensland and the Wide Bay region. Very heavy rainfall affected the Gold Coast, while Brisbane experienced high winds, and a storm cell produced giant hail 8 cm to 10 cm in diameter at Wolvi and Wilsons Pocket (east-northeast of Gympie), and hail up to 11.5 cm in diameter at Goomboorian. There were unconfirmed reports of hail up to 13 cm in diameter at near Gympie. Hail of such large sizes is very rare in Australia.

Area-average rainfall
	Rank (of 120)	Average (mm)	Departure from mean	Comment
Australia	1	15.4	−70%	lowest
Queensland	2	20.1	−76%	2nd lowest (record 19.6 mm in 1938)
New South Wales	2	7.8	−86%	2nd lowest (record 6.0 mm in 1938)
Victoria	3	10.6	−78%	3rd lowest (record 3.6 mm in 1972)
Tasmania	46	84.8	−19%
South Australia	12	3.9	−79%
Western Australia	18	15.4	−52%
Northern Territory	4	20.2	−73%	4th lowest (record 16.3 mm in 1938)
Murray-Darling Basin	2	6.1	−87%	2nd lowest (record 3.8 mm in 1938)

Rank ranges from 1 (lowest) to 120 (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
	Totals	Percentages	Deciles
Total rainfall

Temperatures Rainfall Extremes Important notes the top

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Australian weather extremes during December 2019
Hottest day	49.9 °C	at Nullarbor (SA) on the 19th
Coldest day	−1.0 °C	at Thredbo AWS (NSW) on the 2nd
Coldest night	−4.0 °C	at kunanyi (Mount Wellington Pinnacle) (Tas.) on the 4th
Warmest night	36.0 °C	at Walungurru Airport (NT) on the 26th
Wettest day	163.2 mm	at Proserpine Airport (Qld) on the 29th

Temperatures Rainfall Extremes Important notes the top

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