Average temperature trends across Western Australia
The temperature averages have been extracted from the database publicly available at the Australian Bureau of Meteorology Climate Data Online platform 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 since 1910. Average mean minimum and maximum temperatures are calculated from May 2021 to April 2022, 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.
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 31 locations across Western Australia
Late 1800s/early 1900s minima - 406.1 / 31 = 13.10
Late 1800s/early 1900s maxima - 783.90 / 31 = 25.29 Note: Busselton weather station closed in November 2011 and all temperatures below from December 2011 are sourced to Busselton Aero. Read more ... Note: Halls Creek Airport 2012 was renamed Halls Creek Meteorological Office and a new Halls Creek Airport 2079 became the primary site from 12 January 2017. To preserve location continuity, data for this page was sourced from site 2012 until December 2018 when the site ceased observations. Note: The Bureau of Meteorology failed to record minimum temperatures at Donnybrook 9534 from September 2019 to August 2021 and these missing values have an influence on the total averages calculated on this page. Donnybrook is a comparatively cool location and the site's missing year of minima means that annual minimum averages for all of WA and grouped sites in 2020/21 are not reliable. Note: The Bureau of Meteorology closed Wiluna 13012 in October 2020 and since then temperatures are from Wiluna Airport 13044. Parallel observations suggest the airport location is 0.1C warmer annually, and this may affect temperature averages on this page. Note: The Bureau of Meteorology failed to record any temperatures during different and/or consecutive months at Balladonia, Donnybrook and Kellerberrin during 2021/22, meaning their 12 month readings are unreliable. Balladonia and Donnybrook are in the comparatively cool south of WA and these missing values have an influence on the total averages calculated on this page. 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. 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 2,092,649 in 2022) had the highest averaged increase in mean maximum temperature among all 31 locations, including pre-1910 data, over the hundred years. 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 climate 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. Coastal locations with 2022 population above 20,000
Late 1800s/early 1900s minima - 58.90 / 5 = 11.78 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).
Late 1800s/early 1900s maxima - 109.50 / 5 = 21.90 Coastal locations with 2022 population below 20,000
Late 1800s/early 1900s minima - 174.70 / 11 = 15.88 Maxima Late 1800s/early 1900s maxima - 285.20 / 11 = 25.93 Inland temperatures
Late 1800s/early 1900s minima - 172.5 / 15 = 11.50 Maxima Late 1800s/early 1900s maxima - 389.2 / 15 = 25.95 All locations except the five urban hot spots
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 26 locations are in the coastal southern half of Western Australia, which is much cooler than the northern half and/or inland throughout the year.
Late 1800s/early 1900s minima - 347.20 / 26 = 13.35
Maxima Late 1800s/early 1900s maxima - 674.40 / 26 = 25.94
Earliest colonial climate data compared to the latest RAW data
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 13 locations from February 2021 to January 2022, the average minimum is 0.94 degrees C warmer than 1876-1899 at 14.44 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 13 locations from February 2021 to January 2022, the average maximum is 0.88 degrees C warmer than 1876-1899 at 25.67 degrees C.
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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