Australia's hottest raw mean monthly temperatures per year

Monthly mean minimum and maximum raw temperatures were downloaded from the Bureau of Meteorology's Climate Data Online for the ACORN weather station network starting in 1910.

There are 1,344 hottest/warmest ever temperature months at the 112 ACORN locations, derived from 209 different weather stations. The CDO raw temperatures are mostly accurate copies of Fahrenheit and Celsius recordings by weather station observers since 1910, although the BoM has made some adjustments.

The highest ever temperature for each of the 12 months at all stations was determined and sorted to establish how many unbroken minimum and maximum hottest/warmest records were set in each year at all weather stations.

There were 112 ACORN locations recording temperatures from 1975 to 2014. These included 69 locations that were operating or opened from 1910-15.

69 vs 112

Results are organised below showing the yearly totals of hottest mean monthly records only among the 69 weather stations open from 1910/15 to 2014. Below this are yearly totals of hottest mean monthly records among all 112 locations operating in 2014, regardless of start date.

Also examined are record hot Januarys, record hot months for inland and coastal weather stations, and a breakdown of records in all states and territories from the respective datasets of 112 and 69 ACORN locations.

With 112 weather stations in the ACORN network since 1975, declining progressively to 69 in 1910/15, it is inevitable that more record hot mean months will occur among the greater number of weather stations.

For a comparison of monthly record mean monthly temperature totals in Australian communities starting 1910, the only legitimate results are at the 69 weather stations logging temperatures from 1910 to 2014.

Note: annual data for 2013 is incomplete because at mid April 2014 the BoM hadn't yet posted all monthly means with many station records only updated to mid 2013, which is said to be Australia's warmest year on record. The BoM claims September 2013 was the hottest ever so the annual total is likely to be bigger when fully collated. However, all stations have monthly maxima records for January 2013, said to be the hottest month in Australian history.

All 69 ACORN locations open since 1910/15

From 1910-1961 there were 350 record maxima monthly temperatures with an average of 30.0C.

From 1962-2013 there were 478 record maxima monthly temperatures with an average of 28.0C.

From 1910-1961 there were 262 record minima monthly temperatures with an average of 16.2C.

From 1962-2013, there were 565 record minimum monthly temperatures with an average of 16.9C.

With record hot minima and maxima combined, there were 76 hottest months in 2005 and 72 in 1914.

Januarys at all 69 ACORN locations open since 1910/15

Among the 69 record hot January maxima at all ACORN stations open since 1910, there were seven in 1939, four in 1932, four in 1947, four in 2001, three in 1929, three in 2006 and three in 2010.

Among the 69 record hot January minima at all ACORN stations open since 1910, there were 10 in 1939, 10 in 2006, six in 2001, four in 1999, three in 1981, three in 1987, three in 1994 and three in 2012.

Combining minima and maxima monthly Januarys, there were 17 records established in 1939 and 13 in 2006, seven in 2001, four in 1932, four in 1947, four in 1999, three in 1929, three in 1981, three in 1987, three in 1994, three in 2006, three in 2010 and three in 2012.

Mean monthly records for inland and coastal stations open since 1910/15

* Coastal weather stations include all major Australian capital cities.

The 39 inland ACORN locations open since 1910/15 collectively recorded 50 hottest ever mean minima and maximum months in 1914.

Since the year 2000, the highest collective annual number of hottest/warmest mean months at the same 39 inland ACORN weather stations was 39 in 2005.

From 1910-1961 there were 243 record maxima mean monthly temperatures at the 39 inland ACORN locations open since 1910.

From 1962-2013 there were 225 record maxima mean monthly temperatures at the 39 inland ACORN locations open since 1910.

From 1910-1961 there were 159 record minima monthly temperatures at the 39 inland ACORN locations open since 1910.

From 1962-2013 there were 309 record minima monthly temperatures at the 39 inland ACORN locations open since 1910.

From 1910-1961 there were 115 record maxima monthly temperatures at the 30 coastal ACORN locations open since 1910.

From 1962-2013 there were 245 record maxima monthly temperatures at the 30 coastal ACORN locations open since 1910.

From 1910-1961 there were 103 record minima monthly temperatures at the 30 coastal ACORN locations open since 1910.

From 1962-2013 there were 257 record minima monthly temperatures at the 30 coastal ACORN locations open since 1910.

From 2000 to 2013 there were 34.4% more record hot mean minimum and maximum months at coastal stations than at inland stations open since 1910 (250 coastal, 186 inland).

Highest number of record months at all 69 ACORN locations open since 1910 in different Australian states and territories:

Queensland Excel download (250kb)

New South Wales Excel download (242kb)

Victoria Excel download (139kb)

South Australia Excel download (131kb)

Western Australia Excel download (242kb)

Northern Territory Excel download (90kb)

Tasmania Excel download (78kb)

Within state and territory subsets of ACORN stations open since 1910 for hottest/warmest maximum and minimum monthly mean temperatures, 78 happened in 1914, 77 in 2005 and 2009, 52 in 1988, 47 in 2010, 46 in 2006, 45 in 2007, 40 in 1998, 37 in 1915 and 30 in 2013.

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All 112 ACORN locations in all years and months

Far more hot/warm monthly temperature records have been broken since 2000 than in previous decades, confounding factors including the advent of Automatic Weather Stations in the 1990s and the Urban Heat Island influence in major cities and regional towns.

From 1910-1961 there were 417 record maximum monthly temperatures with an average of 29.5C.

From 1962-2013, there were 927 record maximum monthly temperatures with an average of 28.2C.

From 1910-1961, there were 323 record minimum monthly temperatures with an average of 16.3C.

From 1962-2013, there were 1,021 record minimum monthly temperatures with an average of 16.3C.

Januarys at all 112 ACORN locations open in 2014

Among the 112 record hot January maxima at all ACORN stations, there were 12 in 2001, eight in 2010, seven in 1939, six in 2006, six in 1947, five in 2013, four in 2005, four in 1994 and four in 1932.

Among the 112 record hot January minima at all ACORN stations, there were 18 in 2006, 13 in 1939, 10 in 2001, six in 2011 and two in 2013.

Combining minima and maxima monthly Januarys, there were seven records established in 2013, 24 in 2006, 22 in 2001 and 20 in 1939.

Mean monthly records for all 112 inland and coastal station open in 2014

* Coastal weather stations include all major Australian capital cities.

From 1910-1961 there were 283 record maximum monthly temperatures at all inland ACORN locations.

From 1962-2013 there were 509 record maximum monthly temperatures at all inland ACORN locations.

From 1910-1961 there were 197 record minimum monthly temperatures at all inland ACORN locations.

From 1962-2013 there were 595 record minimum monthly temperatures at all inland ACORN locations.

From 1910-1961 there were 134 record maximum monthly temperatures at all coastal ACORN locations.

From 1962-2013 there were 418 record maximum monthly temperatures at all coastal ACORN locations.

From 1910-1961 there were 126 record minimum monthly temperatures at all coastal ACORN locations.

From 1962-2013 there were 426 record minimum monthly temperatures at all coastal ACORN locations.

From 2000-13 there were 33.8% more record hot mean minimum and maximum months at coastal stations than at inland stations (249 coastal, 186 inland).

Highest number of record months at all 112 ACORN locations in different Australian states and territories:

Queensland Excel download (250kb)

New South Wales Excel download (242kb)

Victoria Excel download (139kb)

South Australia Excel download (131kb)

Western Australia Excel download (242kb)

Northern Territory Excel download (90kb)

Tasmania Excel download (78kb)

Having the highest number of mean monthly temperatures in a year does not mean that year was necessarily the hottest since 1910 as warm averages in other months might result in a higher overall annual average.

However, the comparison of 69 weather stations operating throughout 1910-2014 does show which years within the ACORN network spanning Australia experienced the largest numbers of record hot/warm mean monthly temperatures.

Inland ACORN stations (10km+ from coast) Excel download (541kb)

Alice Springs, Amberley, Barcaldine, Bathurst, Birdsville, Boulia, Bourke, Bridgetown, Butlers Gorge, Cabramurra, Camooweal, Canberra, Charleville, Charters Towers, Cobar, Cunderdin, Dalwallinu, Deniliquin, Dubbo, Forrest, Gayndah, Georgetown, Giles, Gunnedah, Halls Creek, Inverell, Kalgoorlie, Katanning, Kerang, Kyancutta, Laverton RAAF, Longreach, Marble Bar, Marree, Meekatharra, Merredin, Mildura, Miles, Morawa, Moree, Mt Gambier, Nhill, Normanton, Nuriootpa, Oodnadatta, Palmerville, Rabbit Flat, Richmond NSW, Richmond Qld, Rockhampton, Rutherglen, Scone, Snowtown, St George, Tarcoola, Tennant Creek, Thargomindah, Tibbooburra, Victoria River, Wagga Wagga, Walgett, Wandering, Wilcannia, Wittenoom, Woomera, Wyalong

Coastal ACORN stations (within 10km of coast) Excel download (406kb)

Adelaide, Albany, Brisbane, Broome, Bundaberg, Burketown, Cairns, Cape Borda, Cape Bruny, Cape Leeuwin, Cape Moreton, Cape Otway, Carnarvon, Ceduna, Coffs Harbour, Darwin, Eddystone, Esperance, Eucla, Gabo Island, Geraldton, Grove, Hobart, Horn Island, Kalumburu, Launceston, Learmonth, Low Head, Mackay, Melbourne, Moruya Heads, Nowra, Orbost, Perth, Point Perpindicular, Port Hedland, Port Lincoln, Port Macquarie, Robe, Sale, Sydney, Townsville, Weipa, Williamtown, Wilsons Promontory, Yamba

Methodology

Mean maximum and minimum temperatures for each of the 12 months at 209 different stations within the 112 ACORN locations were downloaded as csv files from the Bureau of Meteorology's Climate Data Online. Their month and temperature columns were ordered chronologically and ascending, with the warmest temperature extracted for each month. All stations that started after 1915 were excluded and the same methodology was used to count the number of warmest months recorded each year at the 69 ACORN locations logging temperatures since 1910-15.

Downloads

Excel with all 209 stations broken into time series and cumulative of all months at all stations (717kb)

Excel with all 112 ACORNS tabulated for monthly maxima records (401kb)

Excel with all 112 ACORNS tabulated for monthly minima records (242kb)

Excel with all 69 ACORN locations open since 1910 (164kb)

Excel with all 69 ACORN locations open since 1910 tabulated for monthly maxima records (229kb)

Excel with all 69 ACORN locations open since 1910 tabulated for monthly minima records (229kb)

Note

The spreadsheet calculation of highest monthly temperatures at all ACORN stations excludes all years before 1910, dismissing an unknown number of stations with unbroken record mean monthly temperatures that may have been set before that year. The deletion of pre-1910 records includes weather stations known to be using a Stevenson Screen since the 19th century, and many highest monthly means listed at CDO differ from results in this analysis because many records were established before 1910 (e.g. Yamba). Where two or more different years share the same record temperature for any particular month, their order is chronological and the most recent is always chosen in favour of older years, creating a bias toward the number of record months in more recent years. When all months at all stations at ACORN locations are calculated and have overlapping years of recording, they are all counted. This creates instances of a potential record mean temperature at two different stations (usually PO and airport) in the same month at the same ACORN location and almost all overlaps occur in the latter half of the 20th century, creating a bias towards the number of record months in more recent years.

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