Average temperature trends across Western Australia
Below is an approximate 100 year comparison of average annual mean minimum and maximum temperatures at 32 different locations across Western Australia, including weather in the capital city of Perth.
The temperature averages have been extracted from the database publicly available at the Australian Bureau of Meteorology website for Western Australia, and from the first ever climate study conducted in the colony of Western Australia before 1900.
The annual mean minimum and maximum data are also linked below where available at locations surveyed by the Bureau of Meteorology in its analysis of "corrected" temperature trends from 1910 to 2008.
Average mean minimum and maximum temperatures are calculated from May 2012 to April 2013, the most recent 12 month timeframe. Albeit accurate, this recent 12 month data for each location should be considered statistically unreliable due to its brevity compared with "climate normals" that have typical year-to-year weather variations smoothed over standard periods (commonly 30 years).
This page is designed to provide a simple, convenient tool for people to observe temperature trends since weather records began in Western Australia, particularly in the context of perceived climate change.
Spotlights
The state of Western Australia covers 2,532,400 square kilometres and was proclaimed a British colony in 1829. The eastern border is 1,862 kilometres long and there is 12,889 kilometres of coastline. The highest elevation is Mt Meharry at 1,249 metres (4,098 feet). Western Australia had a population of 2.2 million in 2009, an increase of 17% since 2000.
Western Australia's capital of Perth is said to be on the coalface of global climate change, with 2007 Australian of the Year and Climate Change Commission chairman Tim Flannery predicting in 2004 that it may become the first city in the world to become a ghost metropolis due to lack of water (BBC, Sydney Morning Herald).
Combined average mean temperatures in all 32 locations across Western Australia
Albany, Balladonia, Bridgetown, Broome, Bunbury, Busselton, Cape Leeuwin, Cape Naturaliste, Carnarvon, Derby, Donnybrook, Esperance, Eucla, Eyre, Geraldton, Halls Creek, Kalgoorlie, Katanning, Kellerberrin, Laverton, Marble Bar, Merredin, Mt Barker, Northam, Onslow, Perth, Rottnest Island, Southern Cross, Wandering, Wiluna, Wyndham, York
Minima
Late 1800s/early 1900s minima - 415 / 32 = 12.96
Late 1900s/early 2000s minima - 431.8 / 32 = 13.52
May 2012 - April 2013 minima - 439.9 / 32 = 13.75
- Average mean minimum in all 32 locations combined has risen 0.56 degrees C from early to late 20th century
- Average mean minimum in all 32 locations combined has risen 0.79 degrees C from early 1900s to 2013
Maxima
Late 1800s/early 1900s maxima - 804.1 / 32 = 25.12
Late 1900s/early 2000s maxima - 820.8 / 32 = 25.64
May 2012 - April 2013 maxima - 853.8 / 32 = 26.68
- Average mean maximum in all 32 locations combined has risen .52 degrees C from early to late 20th century
- Average mean maximum in all 32 locations combined has risen 1.56 degrees C from early 1900s to 2013
Note: these calculations exclude February 2011 for Marble Bar, which the Bureau of Meteorology reports had no data available for the month. February 2011 temperatures for Marble Bar are similarly missing from all calculations below.
Note: Busselton weather station closed in November 2011 and all temperatures below from December 2011 are sourced to Busselton Aero. Read more ...
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Hot spots
It should be noted that city and large town temperature readings may be influened by urban heat islands.
Also, it is difficult to compare all locations in Western Australia without accounting for temperatures in coastal cities and towns that are strongly influenced by ocean proximity. Overnight minima in coastal locations are several degrees warmer than inland locations because of the thermal blanket created by the ocean, and strong sea breezes reduce daytime temperatures along much of Western Australia's coastline during early-mid summer.
These natural variables have little impact on inland temperatures and this may influence comparative locational analysis.
About 83% of Western Australia's total population live in the 15 coastal cities and towns with temperatures recorded by the Australian Bureau of Meteorology since the year 1900.
The five coastal locations in Western Australia with populations above 20,000 (Albany, Bunbury, Busselton, Geraldton, Perth) have been major and expanding urban centres since colonial settlement in the early 19th century. Not surprisingly, the capital city of Perth (population 1.6 million in 2009) had the highest averaged increase in mean maximum temperature among all 32 locations, including pre-1910 data, over the hundred years (1.7 degrees C). However, it should be noted that changes in temperature recording location from Mt Eliza near the central city to the northern suburb of Mt Lawley mean Perth only has a reliable history beginning in 1994.
A temperature history comparison between the five large coastal centres and all other surveyed coastal locations suggests that the heat sink created by population and social infrastructure adds between .5 and 1 degree C to daytime maximum temperatures.
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Coastal locations with 2006 population above 20,000
Albany, Bunbury, Busselton, Geraldton, Perth
Minima
Late 1800s/early 1900s minima - 58.9 / 5 = 11.78
Late 1900s/early 2000s minima - 62.66 / 5 = 12.53
May 2012 - April 2013 minima - 62.36 / 5 = 12.47
- Average mean minimum in 5 locations combined has risen .81 degrees C from early to late 20th century
- Average mean minimum in 5 locations combined has risen .69 degrees C from early 1900s to 2013
Note: Minima are affected by relocation of temperature ground stations in all five large coastal locations during the 20th century, with consequent falls in recorded overnight minima due to greater distance from the ocean and removal of the urban heat influence. Check all five locations below (except Busselton) to confirm significant falls in minima coinciding with ground station relocations (Albany, Bunbury, Busselton, Geraldton, Perth).
Maxima
Late 1800s/early 1900s maxima - 109.5 / 5 = 21.90
Late 1900s/early 2000s maxima - 115 / 5 = 23
May 2012 - April 2013 maxima - 120.9/ 5 = 24.18
- Average mean maximum in 5 locations combined has risen 1.10 degrees C from early to late 20th century
- Average mean maximum in 5 locations combined has risen 2.28 degrees C from early 1900s to 2013
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Coastal locations with 2006 population below 20,000
Broome, Cape Leeuwin, Cape Naturaliste, Carnarvon, Derby, Esperance, Eucla, Eyre, Onslow, Rottnest Island, Wyndham
Minima
Late 1800s/early 1900s minima - 174.8 / 11 = 15.89
Late 1900s/early 2000s minima - 180.3 / 11 = 16.39
May 2012 - April 2013 minima - 181.39 / 11 = 16.49
- Average mean minimum in 11 locations combined has risen .5 degrees C from early to late 20th century
- Average mean minimum in 11 locations combined has risen .60 degree C from early 1900s to 2012
Maxima
Late 1800s/early 1900s maxima - 285.8 / 11 = 25.98
Late 1900s/early 2000s maxima - 291.5 / 11 = 26.5
May 2012 - April 2013 maxima - 304.24 / 11 = 27.66
- Average mean maximum in 11 locations combined has risen .52 degrees C from early to late 20th century
- Average mean maximum in 11 locations combined has risen 1.68 degrees C from early 1900s to 2013
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Inland temperatures
16 remaining inland towns
Balladonia, Bridgetown, Donnybrook, Halls Creek, Kalgoorlie, Katanning, Kellerberrin, Laverton, Marble Bar, Merredin, Mt Barker, Northam, Southern Cross, Wandering, Wiluna, York
Minima
Late 1800s/early 1900s minima - 181.4 / 16 = 11.33
Late 1900s/early 2000s minima - 193 / 16 = 12.06
May 2012 - April 2013 minima - 196.18 / 16 = 12.26
- Average mean minimum in 16 inland locations combined has risen .73 degrees C from early to late 20th century
- Average mean minimum in 16 inland locations combined has risen .93 degrees C from early 1900s to 2013
Maxima
Late 1800s/early 1900s maxima - 409.1 / 16 = 25.56
Late 1900s/early 2000s maxima - 412.6 / 16 = 25.78
May 2012 - April 2013 maxima - 428.65 / 16 = 26.79
- Average mean maximum in 16 inland locations combined has risen .22 degrees C from early to late 20th century
- Average mean maximum in 16 inland locations combined has risen 1.23 degrees C from early 1900s to 2013
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All locations except the five urban hot spots
Balladonia, Bridgetown, Broome, Cape Leeuwin, Cape Naturaliste, Carnarvon, Derby, Donnybrook, Esperance, Eucla, Eyre, Halls Creek, Kalgoorlie, Katanning, Kellerberrin, Laverton, Marble Bar, Merredin, Mt Barker, Northam, Onslow, Rottnest Island, Southern Cross, Wandering, Wiluna, Wyndham, York
Alternatively, the five major towns and cities can be compared with all 27 coastal and inland locations over 100 years.
As well as coastal vs inland natural variables, this comparison should create an upward bias on averages because all five towns and cities excluded from the 27 locations are in the coastal southern half of Western Australia, which is much cooler than the northern half and/or inland throughout the year.
Minima
Late 1800s/early 1900s minima - 356.1 / 27 = 13.18
Late 1900s/early 2000s minima - 372.6 / 27 = 13.83
May 2012 - April 2013 minima - 377.57 / 27 = 13.98
- Average mean minimum in 27 locations combined has risen .65 degrees C from early to late 20th century - compared to a rise of .56 degrees C for all 32 locations including Albany, Bunbury, Busselton, Geraldton, Perth (these five locations alone increased .68 degrees C).
- Average mean minimum in 27 locations combined has risen .80 degrees C from early 1900s to 2013 - compared to a rise of 0.79 degrees C for all 32 locations including Albany, Bunbury, Busselton, Geraldton, Perth (these five locations alone rose .55 degrees C).
Maxima
Late 1800s/early 1900s maxima - 694.6 / 27 = 25.72
Late 1900s/early 2000s maxima - 704.5 / 27 = 26.08
May 2012 - April 2013 maxima - 732.92 / 27 = 27.15
- Average mean maximum in 27 locations combined has risen .36 degrees C from early to late 20th century - compared to a rise of .52 degrees C for all 32 locations including Albany, Bunbury, Busselton, Geraldton, Perth (these five locations alone increased 0.56 degrees C).
- Average mean maximum in 27 locations combined has risen 1.43 degrees C from early 1900s to 2013 - compared to a rise of 1.56 degrees C for all 32 locations including Albany, Bunbury, Busselton, Geraldton, Perth (these five locations alone increased 2.18 degrees C).
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Bureau of Meteorology "high quality" data since 1910
For 26 locations in Western Australia, the Bureau of Meteorology provides "high quality" annual data since 1910.
The bureau states that weather recordings prior to 1910 are unreliable for comparison. Regulated recording methods were introduced as of 1910 and the data the bureau supplies has been homogenized and corrected to account for artificial factors such as changes in site location, exposure, instrumentation or observation procedures (... more).
Twenty of these locations are among the 32 surveyed by this web page and their annual temperature data files (1910-2010) are linked below, including averaged 30 year temperatures from 1910 to 1939 and from 1980 to 2009, plus charts of min/mean/max temperatures since 1910:
Coastal:
Albany Airport minimum / mean / maximum / temperature chart 1910-2010
Broome Airport minimum / mean / maximum / temperature chart 1910-2010
Cape Leeuwin minimum / mean / maximum / temperature chart 1910-2010
Cape Naturaliste minimum / mean / maximum / temperature chart 1910-2010
Carnarvon Airport minimum / mean / maximum / temperature chart 1910-2010
Derby Aero minimum / mean / maximum / temperature chart 1910-2010
Esperance minimum / mean / maximum / temperature chart 1910-2010
Geraldton Airport minimum / mean / maximum / temperature chart 1910-2010
Perth Airport minimum / mean / maximum / temperature chart 1910-2010
Rottnest Island minimum / mean / maximum / temperature chart 1910-2010
Inland:
Bridgetown Post Office minimum / mean / maximum / temperature chart 1910-2010
Halls Creek Airport minimum / mean / maximum / temperature chart 1910-2010
Kalgoorlie-Boulder Airport minimum / mean / maximum / temperature chart 1910-2010
Katanning minimum / mean / maximum / temperature chart 1910-2010
Kellerberrin minimum / mean / maximum / temperature chart 1910-2010
Marble Bar minimum / mean / maximum / temperature chart 1910-2010
Merredin minimum / mean / maximum / temperature chart 1913-2010
Southern Cross minimum / mean / maximum / temperature chart 1910-2010
Wandering minimum / mean / maximum / temperature chart 1910-2010
York minimum / mean / maximum / temperature chart 1910-2010
Following is a summary of "high quality" data for the 20 locations:
Minima
- For all 20 locations, the average mean minimum has risen .7 degrees C from 1910-1939 to 1981-2010
- For 10 coastal locations, the average mean minimum has risen .64 degrees C from 1910-1939 to 1981-2010
- For 10 inland locations, the average mean minimum has risen .76 degrees C from 1910-1939 to 1981-2010
Maxima
- For all 20 locations, the average mean maximum has risen .61 degrees C from 1910-1939 to 1981-2010
- For 10 coastal locations, the average mean maximum has risen .54 degrees C from 1910-1939 to 1981-2010
- For 10 inland locations, the average mean maximum has risen .68 degrees C from 1910-1939 to 1981-2010
The Bureau of Meteorology also maintains six other high quality climate sites in Western Australia with temperature records not dating back to 1900. Temperature history charts have been created for these locations - Giles Meteorological Office, Jarrahwood, Meekathara Airport, Newman Aero, Port Hedland, Roebourne.
A chart is available to see all 26 high quality recording sites maintained across Western Australia by the Bureau of Meteorology with minimum, mean and maximum temperatures averaged every year for all locations from 1910 to 2009.
For more recent temperatures, a chart is available to see all 26 high quality recording sites maintained across Western Australia by the Bureau of Meteorology with minimum, mean and maximum temperatures averaged every year for all locations from 1979 to 2009.
Comparing 1979-1989 with 1999-2009, the average mean temperature across all 26 "high quality" locations increased by 0.197C over the 31 year period. Comparing 1990-1999 with 2000-2009, the average mean temperature across all 26 "high quality" locations fell by 0.0006C.
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Earlier data compared to latest "corrected" data
Although the pre-1910 temperature recordings in each location examined below are considered by the Bureau of Meteorology to be unreliable compared to the regulated post-1910 data, it is still worth comparing these earliest temperatures with the most recent "corrected" data from 1979-2008 in the 20 locations.
Minima
- For all 20 locations, the average mean minimum rose .44 degrees C from ~1900 to 1979-2008
- For 10 coastal locations, the average mean minimum rose .29 degrees C from ~1900 to 1979-2008
- For 10 inland locations, the average mean minimum rose .58 degrees C from ~1900 to 1979-2008
Maxima
- For all 20 locations, the average mean maximum rose .48 degrees C from ~1900 to 1979-2008
- For 10 coastal locations, the average mean maximum rose .86 degrees C from ~1900 to 1979-2008
- For 10 inland locations, the average mean maximum rose .10 degrees C from ~1900 to 1979-2008
Temperature data is adjusted by various authorities due to perceived artificial factors such as changes in site location, exposure, instrumentation or observation procedures, etc, and the accuracy of all data sets is controversial. See the different historic trends interpreted for Albany, Broome, Cape Leeuwin, Cape Naturaliste, Carnarvon, Derby, Esperance, Geraldton, Halls Creek, Kalgoorlie, Katanning, Kellerberrin, Marble Bar, Merredin, Perth, Rottnest Island, Southern Cross, Wandering and York.
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Earliest colonial climate data compared to the latest quality data
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The West Australian colony's earliest known meteorological analysis is The Climate of Western Australia 1876-1899 (PDF 25.4mb) compiled in 1901 by then Government Astronomer William Ernest Cooke. This document contains raw, unregulated data that is considered unreliable.
As the Government Astronomer explains in this historic document: "... it may be safely assumed that the results in this document give a close approximation to the truth; sufficiently so for all practical purposes, but scarcely to be considered quite accurate enough for the scientist."
Nevertheless, this compilation contains the only known official climate records for the Western Australia colony before 1900 and although recording discrepancies may have been common, these mistakes might either inflate or deflate the real temperatures (e.g. thermometers near warm buildings or in cool locations, although a common error was heat radiation from the ground).
The pre-1900 records are thus worth comparing with the most recent 30 years of regulated quality data from the Bureau of Meteorology, if only out of curiosity. See a detailed breakdown comparison of temperatures from the Cooke document.
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 (PDF 25.4mb)
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Minima
Towns surveyed for mean minimum night temperatures by the Government Astronomer that are included in the Bureau of Meteorology's quality control sites include Albany (11.4 C), Broome (20.1 C), Cape Leeuwin (14 C), Carnarvon (16 C), Derby (21 C), Esperance (11.3 C), Geraldton (13.9 C), Kalgoorlie (12.2 C), Katanning (8.4 C), Perth (12.3 C), Rottnest (13.3 C), Southern Cross (10.2 C) and York (11 C).
Combined, these 13 pre-1900 minima average 13.5 degrees C. Combining the same locations among the Bureau's quality controlled sites from 1979 to 2008, the average minimum is .37 degrees C warmer than 1876-1899 at 13.87 degrees C.
Combining the same 13 locations from May 2012 to April 2013, the average minimum is .90 degrees C warmer than 1876-1899 at 14.24 degrees C.
Maxima
Towns surveyed for mean maximum day temperatures by the Government Astronomer that are included in the Bureau of Meteorology's quality control sites include Albany (18.5 C), Broome (31.7 C), Cape Leeuwin (19.6 C), Carnarvon (28.7 C), Derby (33.7 C), Esperance (21.4 C), Geraldton (24.5 C), Kalgoorlie (25.5 C), Katanning (22.5 C), Perth (24.2 C), Rottnest, (22.2 C), Southern Cross (26 C) and York (24 C).
Combined, these 13 pre-1900 maxima average 24.80 degrees C. Combining the same locations among the Bureau's quality controlled sites from 1979 to 2008, the average maximum is .34 degrees C warmer than 1876-1899 at 25.14 degrees C.
Combining the same 13 locations from May 2012 to April 2013, the average maximum is 1.35 degrees C warmer than 1876-1899 at 26.05 degrees C.
Another historic document analysing Western Australia's past climate is Results of Meteorological Observations in Western Australia during 1908 (PDF 28mb) published in 1912 by then Commonwealth Meteorologist Henry Ambrose Hunt. Also of interest is The Climate and Weather of Australia (PDF 29mb), the first textbook on Australian Meteorology, published in 1913 by Henry Hunt and associates. See Hunt vs BoM temperature comparison for Australian capital cities.
For locations below that were monitored by Government Astronomer William Ernest Cooke, his recordings are listed as Pre-1900 vs recent 30 years mean temperature.
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Balladonia (BoM station 11017)
(elevation 151m, population 2006 - 50)
1891-1920 (20 years surveyed)
Average mean minimum 9.7
Average mean maximum 23.8
1921-1943 (22 years) / min 9.6 / max 24.2
1931-1943 (12 years) / min 9.5 / max 24.2
1951-1980 (16 years) / min 9.9 / max 25.1
1965-1990 (25 years) / min 9.9 / max 25.2
1971-2000 (30 years) / min 10.0 / max 25.3
1981-2010 (30 years)
Average mean minimum 10.1
Average mean maximum 25.3
12 months May 2012 - April 2013
Mean annual minimum 10.7
Mean annual maximum 25.6
BoM average means all available years
Mean annual minimum 9.8
Mean annual maximum 24.7
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Balladonia aerial picture
BoM historic annual minima from 1901
BoM historic annual maxima from 1901
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Mt Barker (BoM station 9581)
(elevation 300m, shire population 2006 - 2,971)
1905-1920 (16 years surveyed)
Average mean minimum 8.9
Average mean maximum 19.9
1921-1950 (30 years) / min 9.1 / max 19.8
1931-1960 (30 years) / min 9.1 / max 20.0
1941-1970 (30 years) / min 9.3 / max 20.3
1951-1975 (25 years) / min 9.5 / max 20.4
1961-1989 (17 years) / min 9.8 / max 20.6
1971-2000 (17 years) / min 10.1 / max 20.3
1981-2010 (22 years)
Average mean minimum 10.1
Average mean maximum 20.4
12 months May 2012 - April 2013
Mean annual minimum 9.9
Mean annual maximum 21.5
BoM average means all available years
Mean annual minimum 9.4
Mean annual maximum 20.1
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Mt Barker aerial picture
BoM historic annual minima from 1905
BoM historic annual maxima from 1905
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Northam (BoM station 10111)
(elevation 170m, shire population 2006 - 6,009)
1902-1920 (19 years surveyed)
Average mean minimum 10.7
Average mean maximum 25.0
1921-1950 (30 years) / min 11.1 / max 25.1
1931-1960 (30 years) / min 10.9 / max 25.3
1941-1970 (30 years) / min 11.0 / max 25.3
1951-1980 (29 years) / min 10.9 / max 25.3
1961-1990 (28 years) / min 11.2 / max 25.4
1971-2000 (28 years) / min 11.2 / max 25.5
1981-2010 (29 years)
Average mean minimum 10.8
Average mean maximum 25.7
12 months May 2012 - April 2013
Mean annual minimum 11.2
Mean annual maximum 26.5
BoM average means all available years
Mean annual minimum 10.9
Mean annual maximum 25.3
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Northam aerial picture
BoM historic annual minima from 1902
BoM historic annual maxima from 1902
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Wiluna (BoM station 13012)
(elevation 521m, shire population 2006 - 681)
1901-1930 (28 years surveyed)
Average mean minimum 14.0
Average mean maximum 28.8
1921-1950 (29 years) / min 14.1 / max 29.1
1931-1960 (30 years) / min 13.9 / max 29.0
1941-1970 (29 years) / min 13.9 / max 29.1
1951-1980 (29 years) / min 14.2 / max 29.1
1961-1990 (29 years) / min 14.7 / max 29.3
1971-2000 (29 years) / min 14.9 / max 29.3
1981-2010 (29 years)
Average mean minimum 14.8
Average mean maximum 29.6
12 months May 2012 - April 2013
Mean annual minimum 15.1
Mean annual maximum 30.8
BoM average means all available years
Mean annual minimum 14.3
Mean annual maximum 29.2
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Wiluna aerial picture
BoM historic annual minima from 1901
BoM historic annual maxima from 1901
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