September 2016 coldest in South West Australia since 1897

September 2016 average temperatures in Perth and across southern Western Australia were the coldest recorded for the month since 1897 in the Bureau of Meteorology's unadjusted raw dataset and the coldest since 1910 in the homegenised ACORN (Australian Climate Observations Reference Network) dataset.

Among the 15 West Australian ACORN stations south of and including Geraldton, the averaged mean raw temperature in September 2016 was 0.28C colder than the previous record coldest September in 1903.

Regardless of how many stations are contributing to the averages in any given year (nine in 1897 increasing to 25 since 1975), mean raw averages show the coldest September was in 2016 at 12.12C, followed by September 1903 at 12.40C, followed by the 118 warmer Septembers.

Six of the 15 stations including Perth had their coldest September mean temperature since 1897, both in the unadjusted raw and homogenised ACORN datasets.

Among the seven ACORN stations south of and including Geraldton that all had a starting year of 1897 (or earlier but using the Perth 1897 benchmark for all stations, meaning it’s highly likely all temperatures were recorded in Stephenson screens), September 2016 was the second coldest since 1897. The seven weather stations averaged 12.38C in September 1992 compared to 12.47C in September 2016, but September 1992 wasn’t the coldest when the eight other stations are included in that year’s averages.

Among the 18 ACORN stations south of and including Carnarvon, September 2016 was the third coldest since 1897 - the 1903 record being 0.08C colder.

Among all 25 WA ACORN stations, September 2016 had the 23rd coldest raw mean temperature since 1897. However, this is a comparison of just nine stations open in 1897 with all 25 as of 1975.

Among all 25 WA ACORN stations across the state, September 2016 was the second coldest since 1975, the coldest being 1978 which was 0.21C colder than September 2016.

Several far northern WA stations had a very hot September 2016, Kalumburu setting a new record mean heat for the month.

Using adjusted ACORN rather than raw temperatures among the 15 WA stations south of and including Geraldton, September 2016 was the coldest since 1910 - beating the previous 1992 record for the coldest September mean by 0.3C based on ACORN adjusted temperatures.

Among the nine ACORN stations south of and including Geraldton that all had a starting year of 1910, September 2016 was the coldest since 1910 using ACORN temperatures (2016 11.83C, 1969 12.06C).

ACORN weather stations:

Albany (start year 1897 in raw and 1910 in ACORN)

4th coldest September mean since 1897 in raw (1969 coldest at 11.20C, 2016 11.42C)

3rd coldest September min since 1897 in raw (1968 coldest at 6.6C, 2016 6.79C)

8th coldest September max since 1897 in raw (1992 coldest at 15.2C, 2016 16.05C)

5th coldest September mean since 1910 in ACORN (1969 coldest at 11.05C, 2016 11.42C)

5th coldest September min since 1910 in ACORN (1952 coldest at 6.2C, 2016 6.79C)

9th coldest September max since 1910 in ACORN (1992 coldest at 15.2C, 2016 16.05C)

Bridgetown (start year 1901 in raw and 1910 in ACORN)

Coldest September mean since 1901 in raw (2016 9.81C, 1969 9.95C)

6th coldest September min since 1901 in raw (1969 coldest at 2.4C, 2016 4.01C)

Equal 2nd coldest September max since 1901 in raw (1917 coldest at 15.5C, 2016 15.6C, 1915 15.6C)

Coldest September mean since 1910 in ACORN (2016 9.81C, 1969 9.85C)

6th coldest September min since 1910 in ACORN (1969 coldest at 2.4C, 2016 4.01C)

Equal coldest September max since 1910 in ACORN (2016 15.6C, 1917 15.6C)

Broome (start year 1897 in raw and 1910 in ACORN)

4th warmest September mean since 1897 in raw (1978 coldest at 23.45C, 2016 25.69C)

2nd warmest September min since 1897 in raw (1946 coldest at 15.9C, 2016 20.92C)

75th coldest September max since 1897 in raw (1997 coldest at 29.2C, 2016 32.26C)

87th coldest September mean since 1910 in ACORN (2004 coldest at 23.70C, 2016 26.59C)

86th coldest September min since 1910 in ACORN (2011 coldest at 17.0C, 2016 20.92C)

71st coldest September max since 1910 in ACORN (1917 coldest at 29.1C, 2016 32.26C)

Cape Leeuwin (start year 1897 in raw and 1910 in ACORN)

4th coldest September mean since 1897 in raw (1971 coldest at 12.95C, 2016 13.15C)

5th coldest September min since 1897 in raw (1971 coldest at 9.9C, 2016 10.47C)

6th coldest September max since 1897 in raw (1917 coldest at 15.5C, 2016 15.82C)

2nd coldest September mean since 1910 in ACORN (1917 coldest at 13.1C, 2016 13.15C)

2nd coldest September min since 1910 in ACORN (1971 coldest at 10.2C, 2016 10.47C)

8th coldest September max since 1910 in ACORN (1915 coldest at 15.3C, 2016 15.82C)

Carnarvon (start year 1897 in raw and 1910 in ACORN)

17th coldest September mean since 1897 in raw (1966 coldest at 17.4C, 2016 18.27C)

9th coldest September min since 1897 in raw (1897 coldest at 9.2C, 2016 12.63C)

42nd coldest September max since 1897 in raw (1915 coldest at 21.9C, 2016 23.91C)

19th coldest September mean since 1910 in ACORN (1915 coldest at 17.15C, 2016 18.27C)

25th coldest September min since 1910 in ACORN (1929 coldest at 11.0C, 2016 12.63C)

25th coldest September max since 1910 in ACORN (1915 coldest at 22.5C, 2016 23.91C)

Cunderdin (start year 1950 in raw and ACORN)

Coldest September mean since 1950 in raw (2016 10.63C, 2009 11.70C)

Coldest September min since 1950 in raw (2016 2.62C, 2010 4.3C)

6th coldest September max since 1950 in raw (1992 coldest at 17.8C, 2016 18.63C)

Coldest September mean since 1950 in ACORN (2016 10.63C, 1968 11.10C)

Coldest September min since 1950 in ACORN (2016 2.62C, 2004 3.4C)

9th coldest September max since 1950 in ACORN (1992 coldest at 17.3C, 2016 18.63C)

Dalwallinu (start year 1955 in raw and 1957 in ACORN)

Coldest September mean since 1955 in raw (2016 11.82C, 1992 12.6C)

Coldest September min since 1955 in raw (2016 4.75C, 2009 6.3C)

2nd coldest September max since 1955 in raw (1992 coldest at 17.9C, 2016 18.89C)

Coldest September mean since 1957 in ACORN (2016 11.82C, 1992 12.6C)

Coldest September min since 1957 in ACORN (2016 4.75C, 2009 6.3C)

2nd coldest September max since 1957 in ACORN (1992 coldest at 17.9C, 2016 18.89C)

Esperance (start year 1897 in raw and 1910 in ACORN)

27th coldest September mean since 1897 in raw (1905 coldest at 11.65C, 2016 13.44C)

38th coldest September min since 1897 in raw (1942 coldest at 6.4C, 2016 8.67C)

23rd coldest September max since 1897 in raw (1992 coldest at 16.3C, 2016 18.2C)

28th coldest September mean since 1910 in ACORN (1969 coldest at 12.35C, 2016 13.44C)

23rd coldest September min since 1910 in ACORN (1942 coldest at 6.8C, 2016 8.67C)

28th coldest September max since 1910 in ACORN (1992 coldest at 16.0C, 2016 18.2C)

Eucla (start year 1910 in raw and ACORN)

17th coldest September mean since 1910 in raw (1958 coldest at 12.25C, 2016 14.27C)

11th coldest September min since 1910 in raw (1931 coldest at6.5C, 2016 7.90C)

39th coldest September max since 1910 in raw (1958 coldest at 17.2C, 2016 20.63C)

11th coldest September mean since 1910 in ACORN (1958 coldest at 12.90C, 2016 14.27C)

13th coldest September min since 1910 in ACORN (1931 coldest at 6.0C, 2016 7.9C)

19th coldest September max since 1910 in ACORN (2010 coldest at 17.8C, 2016 20.63C)

Forrest (start year 1946 in raw and ACORN)

13th coldest September mean since 1946 in raw (1968 coldest at 12.70C, 2016 13.87C)

5th coldest September min since 1946 in raw (1968 coldest at 3.8C, 2016 5.75C)

15th coldest September max since 1946 in raw (2010 coldest at 18.6C, 2016 21.99C)

8th coldest September mean since 1946 in ACORN (2010 coldest at 13.10C, 2016 13.87C)

2nd coldest September min since 1946 in ACORN (1968 coldest at 4.8C, 2016 5.75C)

12th coldest September max since 1946 in ACORN (2010 coldest at 18.6C, 2016 21.99C)

Geraldton (start year 1897 in raw and 1910 in ACORN)

Coldest September mean since 1897 in raw (2016 13.58C, 1966 13.9C)

Coldest September min since 1897 in raw (2016 6.72C, 1967 7.3C)

13th coldest September max since 1897 in raw (1992 coldest at 19.6C, 2016 20.44C)

Coldest September mean since 1910 in ACORN (2016 13.58C, 1966 13.85C)

Coldest September min since 1910 in ACORN (2016 6.72C, 1967 7.3C)

13th coldest September max since 1910 in ACORN (1915 coldest at 19.6C, 2016 20.44C)

Giles (start year 1956 in raw and ACORN)

10th coldest September mean since 1956 in raw (1978 coldest at 16.15C, 2016 18.02C)

5th coldest September min since 1956 in raw (1978 coldest at 9.4C, 2016 10.43C)

14th coldest September max since 1956 in raw (1978 coldest at 22.9C, 2016 25.60C)

8th coldest September mean since 1956 in ACORN (1978 coldest at 16.15C, 2016 18.02C)

6th coldest September min since 1956 in ACORN (1978 coldest at 8.7C, 2016 10.43C)

14th coldest September max since 1956 in ACORN (1978 coldest at 22.9C, 2016 25.60C)

Halls Creek (start year 1898 in raw and 1910 in ACORN)

8th warmest September mean since 1898 in raw (1925 coldest at 21.35C, 2016 28.25C)

6th warmest September min since 1898 in raw (1923 coldest at 11.7C, 2016 21.19C)

16th warmest September max since 1898 in raw (1925 coldest at 30.7C, 2016 35.31C)

11th warmest September mean since 1910 in ACORN (1925 coldest at 23.05C, 2016 28.25C)

7th warmest September min since 1910 in ACORN (1913 coldest at 15.6C, 2016 21.19C)

21st warmest September max since 1910 in ACORN (1925 coldest at 29.9C, 2016 35.31C)

Kalumburu (start year 1941 in raw and ACORN)

Warmest September mean since 1941 in raw (2011 coldest at 25.1C, 2016 30.0C)

2nd warmest September min since 1941 in raw (1958 coldest at 15.0C, 2016 24.1C)

Warmest September max since 1941 in raw (1941 coldest at 33.5C, 2016 37.54C)

Warmest September mean since 1941 in ACORN (2011 coldest at 25.10C, 2016 30.00C)

2nd warmest September min since 1941 in ACORN (1958 coldest at 14.3C, 2016 22.45C)

Warmest September max since 1941 in ACORN (2004 coldest at 33.3C, 2016 37.54C)

Learmonth (start year 1975 in raw and ACORN)

3rd coldest September mean since 1975 in raw (1992 coldest at 19.80C, 2016 20.34C)

Coldest September min since 1975 in raw (2016 12.04, 1993 12.5C)

14th coldest September max since 1975 in raw (1992 coldest at 26.6C, 2016 28.63C)

3rd coldest September mean since 1975 in ACORN (1992 coldest at 19.80C, 2016 20.34C)

Coldest September min since 1975 in ACORN (2016 12.04, 1993 12.5C)

14th coldest September max since 1975 in ACORN (1992 coldest at 26.60C, 2016 28.63C)

Kalgoorlie (start year 1897 in raw and 1910 in ACORN)

5th coldest September mean since 1897 in raw (1992 coldest at 12.00C, 2016 13.09C)

Coldest September min since 1897 in raw (2016 5.72, 1968 6.0C)

13th coldest September max since 1897 in raw (1992 coldest at 17.7C, 2016 20.46C)

2nd coldest September mean since 1910 in ACORN (1992 coldest at 12.40C, 2016 13.09C)

Coldest September min since 1910 in ACORN (2016 5.72, 1919 6.6C)

12th coldest September max since 1910 in ACORN (1992 coldest at 17.70C, 2016 20.46C)

Katanning (start year 1897 in raw and 1910 in ACORN)

Coldest September mean since 1897 in raw (2016 9.61, 1969 10.3C)

2nd coldest September min since 1897 in raw (2010 coldest at 4.0C, 2016 4.14C)

Coldest September max since 1897 in raw (2016 15.08, 1992 15.12C)

Coldest September mean since 1910 in ACORN (2016 9.61C, 1923 10.15C)

2nd coldest September min since 1910 in ACORN (2010 coldest at 4.0C, 2016 4.14C)

3rd coldest September max since 1910 in ACORN (1915 coldest at 14.80C, 2016 15.08C)

Marble Bar (start year 1901 in raw and 1910 in ACORN)

55th coldest September mean since 1901 in raw (coldest 1978 at 22.60C, 2016 25.07C)

72nd coldest September min since 1901 in raw (1903 coldest at 12.6C, 2016 17.12C)

33rd coldest September max since 1901 in raw (1978 coldest at 30.4C, 2016 33.02C)

51st coldest September mean since 1910 in ACORN (1925 coldest at 22.15C, 2016 25.07C)

72nd coldest September min since 1910 in ACORN (1966 coldest at 13.1C, 2016 17.12C)

38th coldest September max since 1910 in ACORN (1925 coldest at 30.60C, 2016 33.02C)

Meekatharra (start year 1927 in raw and ACORN)

13th coldest September mean since 1927 in raw (1931 coldest at 16.2C, 2016 17.10C)

8th coldest September min since 1927 in raw (1931 coldest at 7.6C, 2016 9.64C)

21st coldest September max since 1927 in raw (1992 coldest at 22.7C, 2016 24.55C)

21st coldest September mean since 1927 in ACORN (1992 coldest at 15.40C, 2016 17.10C)

15th coldest September min since 1927 in ACORN (1931 coldest at 8.5C, 2016 9.64C)

36th coldest September max since 1927 in ACORN (1992 coldest at 21.6C, 2016 24.55C)

Merredin (start year 1913 in raw and 1915 in ACORN)

6th coldest September mean since 1913 in raw (1917 coldest at 11.3C, 2016 11.55C)

5th coldest September min since 1913 in raw (1913 coldest at 2.6C, 2016 4.3C)

13th coldest September max since 1913 in raw (1992 coldest at 16.7C, 2016 18.8C)

5th coldest September mean since 1915 in ACORN (1966 coldest at 11.30C, 2016 11.55C)

4th coldest September min since 1915 in ACORN (1919 coldest at 3.0C, 2016 4.3C)

14th coldest September max since 1915 in ACORN (1992 coldest at 16.8C, 2016 18.8C)

Morawa (start year 1925 in raw and ACORN)

2nd coldest September mean since 1925 in raw (1968 coldest at 13.26C, 2016 13.27C)

2nd coldest September min since 1925 in raw (1929 coldest at 5.35C, 2016 5.42C)

11th coldest September max since 1925 in raw (1968 coldest at 19.7C, 2016 21.11C)

4th coldest September mean since 1925 in ACORN (1968 coldest at 12.85C, 2016 13.27C)

Coldest September min since 1925 in ACORN (2016 5.42C, 1929 5.6C)

16th coldest September max since 1925 in ACORN (1992 coldest at 19.1C, 2016 21.11C)

Perth (start year 1897 in raw and 1910 in ACORN)

Coldest September mean since 1897 in raw (2016 13.02C, 1906 13.03C)

Coldest September min since 1897 in raw ((2016 7.6C, 2004 8.0C)

19th coldest September max since 1897 in raw (1915 coldest at 16.8C, 2016 18.5C)

Coldest September mean since 1910 in ACORN (2016 13.02C, 1919 13.10C)

4th coldest September min since 1910 in ACORN (1969 coldest at 6.8C, 2016 7.56C)

4th coldest September max since 1910 in ACORN (1915 coldest at 17.70C, 2016 18.48C)

Port Hedland (start year 1913 in raw and ACORN)

69th coldest September mean since 1913 in raw (1978 coldest at 21.7C, 2016 24.30C)

82nd coldest September min since 1913 in raw ((1966 coldest at 13.0C, 2016 17.08C)

50th coldest September max since 1913 in raw (1915 coldest at 28.1C, 2016 31.51C)

84th coldest September mean since 1913 in ACORN (1978 coldest at 20.95C, 2016 24.30C)

6th warmest September min since 1913 in ACORN (1925 coldest at 12.4C, 2016 17.08C)

53rd coldest September max since 1913 in ACORN (1984 coldest at 28.10C, 2016 31.51C)

Wandering (start year 1902 in raw and 1910 in ACORN)

2nd coldest September mean since 1902 in raw (1903 coldest at 5.6C, 2016 9.32C)

4th coldest September min since 1902 in raw ((1903 coldest at -0.3C, 2016 2.7C)

3rd coldest September max since 1902 in raw (1903 coldest at 11.50C, 2016 15.94C)

2nd coldest September mean since 1910 in ACORN (1969 coldest at 9.20C, 2016 9.32C)

2nd coldest September min since 1910 in ACORN (1969 coldest at 1.8C, 2016 2.70C)

5th coldest September max since 1910 in ACORN (1992 coldest at 15.70C, 2016 15.94C)

Wittenoom (start year 1952 in raw and ACORN)

25th coldest September mean since 1952 in raw (1978 coldest at 21.4C, 2016 23.51C)

25th coldest September min since 1952 in raw ((1953 coldest at 13.5C, 2016 16.24C)

22nd coldest September max since 1952 in raw (1978 coldest at 28.1C, 2016 30.77C)

23rd coldest September mean since 1952 in ACORN (1978 coldest at 21.40C, 2016 23.51C)

24th coldest September min since 1952 in ACORN (1953 coldest at 13.5C, 2016 16.24C)

22nd coldest September max since 1952 in ACORN (1978 coldest at 28.10C, 2016 30.77C)

Perth recorded its coldest mean September temperature since 1897 despite the Urban Heat Island warming of a surrounding capital city and/or international airport.

The coldest ever September in the south of WA was despite 2016 being described as the hottest ever year globally.

BoM estimates

The BoM's September 2016 Monthly Climate Summary for WA lists 31 weather stations that had their coldest ever average minimum, eight that had their coldest ever average maximum, and 26 that had their coldest mean temperature on record.

Five of the six ACORN stations above that in 2016 had record cold September min, max or mean are not included in the BoM lists.

The BoM climate summary only compares September 2016 with the stations' existing short-term location records, most starting within the past 30 years, while the analysis on this page compares ACORN station raw and adjusted temperatures back to 1897.

The climate summary states: "Observations for "Perth Metro" are taken from the current site at Mount Lawley (Bureau number 009225). Comparisons are made against combined data from the current site (which opened in early 1993) and the previous site at Perth Regional Office (009034), which ran from 1876 to early 1992."

The summary lists Perth Metro’s September 2016 minimum of 7.6C as 2.0C below average. Perth Metro 1994-2015 had a mean minimum of 9.6C (9.5C if you include September 2016). The mean minimum of stations 9034 and 9225 from 1897 to 2015 was 10.1C (RO 9034 1897-1991 min was 10.3C). If Perth Metro comparisons are based on combined data from 9225 and 9034, September 2016 was 2.5C below average, not 2.0C.

Click here (2.2mb) for an Excel download containing spreadsheets for all 25 WA ACORN stations with columns of RAW and ACORN minimum, maximum and mean temperatures each year since 1897.

Probable causes

The temperature maps below show global sea surface temperatures each January and September since 2008, with the area of interest to the west and south of Western Australia.

The charts above show Indian and Southern Ocean surface temperatures have tumbled since the beginning of 2016. In late September 2016, southern SST were their coldest and over the broadest area in at least nine years.

The charts below show closer detail of the cold SST formation off the south west coast in February 2016 and its monthly spread to September 2016 when record cold temperatures in southern WA coincided with severe storm, wind and flood damage in South Australia.

Another contributor to the record cold September 2016 in southern WA is the fact that mid-year night temperatures have been getting colder.

The table below is extracted from Australia's 1918 Year Book and shows climatological averages in Perth.

The 1897-1917 monthly temperatures listed above are not within a significant timeframe but allow a useful comparison of recent observations with the first 20 years of Stephenson Screen temperature recordings in Perth. The Fahrenheit temperatures above are mostly in agreement with listings for Perth Regional Office 9034 in the Bureau of Meteorology's Climate Data Online.

The tables below compare the 1897-1917 temperatures with 1994-2015 min and max readings at Perth Metro 9225 and Perth Airport 9021 (ACORN station).

The minima recordings show Perth Metro since 1994 has been cooler at night than it was in 1897-1917 from May to September, with Perth Airport minima cooler than a hundred years ago from April to December.

The 1897-1917 averages are from Kings Park while the 1994-2015 averages are from Mt Lawley or Perth Airport. The location changes are influential but consistent and also applicable to the increasing maxima.

Even with huge cooling ACORN adjustments to most months for the period 1910-1917, the 1994-2015 September average minimum was just 0.2C warmer at Perth Metro and 0.2C cooler at Perth Airport. Even with the cooling ACORN changes, mid-winter July minima was 0.3C warmer at Perth Metro and 0.1C warmer at Perth Airport a hundred years ago.

These figures suggest a long term mid-year cooling in Perth minima, tied to declines in winter rainfall. Combined with very cold SST pushing chilled winds into the west and south of Australia, it is unsurprising that September 2016 was the coldest ever recorded in Perth and the southern half of Western Australia.

Cold temperature update

Before the coldest September on record, southern WA had a very cool winter. Eleven southern WA stations had their lowest winter mean maximum on record and 32 had their lowest winter mean maximum in at least 23 years. Five stations had their lowest mean temperature on record and eight had their lowest mean temperature in at least 20 years.

At Perth Metro 9225 and Perth Regional Office 9034 dating back to 1897, the three months of August, September and October 2016 had the 6th coolest mean, 2nd coolest min and 36th coolest max:

At Perth Airport 9021 dating back to the station's opening in 1944, the three months of August, September and October 2016 had the 4th coolest mean, 5th coolest min and 6th coolest max:

If there are concerns that station relocations since 1897 distort temperature comparisons over time, the Australian Climate Observation Reference Network (ACORN) which determines national policy has adjusted temperatures to compensate for artificial influences such as relocations and the Urban Heat Island effect in central Perth. The adjusted ACORN temperatures back to 1910 show the three months of August, September and October 2016 had the 3rd coolest mean, 6th coolest min and 2nd coolest max:

At Perth Metro 9225 and Perth Regional Office 9034 dating back to 1897, the six months from May to October 2016 had the 7th coolest mean, 4th coolest min and 53rd coolest max:

At Perth Airport 9021 dating back to the station's opening in 1944, the six months from May to October 2016 had the 8th coolest mean, 10th coolest min and 11th coolest max:

ACORN corrected and adjusted temperatures back to 1910 show the six months from May to October 2016 had the 5th coolest mean, 11th coolest min and 6th coolest max:

Summer daily maximum records smashed

On 30 January 2017, Perth Metro 9225 had its fifth coldest January maximum temperature since readings began at Perth Regional Office 9034 in 1897. At Perth Airport 9021, 30 January was the coldest January day since the station opened in 1945.

On 9 February 2017, Perth Metro 9225 had by far its coldest February maximum temperature since readings began at Perth Regional Office 9034 in 1897, smashing the previous record by 1.6C. It was also the coldest February day ever recorded at Perth Airport, the maximum a whopping 2.7C colder than the previous record in 1991. It was also the coldest February day recorded since 1910 at all ACORN-SAT stations in WA (see analysis of coldest February day ever in WA).

On 10 February 2017 at Perth Airport, it was the seventh coldest February day ever recorded. *

In January 2017, 27 northern WA stations had their record highest January daily rainfall, 18 northern WA stations had their record highest January total rainfall, and 24 northern WA stations had their highest January total rainfall for at least 20 years.

In January 2017, seven southern WA stations had their record lowest January daily maximum temperature, three had their lowest January mean daily maximum temperature in at least 20 years, four had their record lowest January temperature, two had their record lowest January mean minimum temperature, and three had their lowest January mean daily minimum temperature in at least 20 years.

* Note: on 10 February 2017, the maximum temperature during daylight hours at Perth Metro was 20.5C, the tenth coldest February day since observations began at Perth Regional Office in 1897. At Perth Airport, the maximum temperature during daylight hours on 10 February 2017 was 20.2C, the third coldest February day since airport observations began in 1945.

However, the maxima recorded by the Bureau of Meteorology for 10 February at Perth Metro were 22.4C at 8.37am on Saturday morning, and at Perth Airport 21.3C at 8.41am on Saturday morning.

The BoM reports daily maximum temperature as the highest temperature in the 24 hours after 9am on any given date. These official temperatures have been used for comparisons in the table above, despite the Friday maxima happening on Saturday morning the following day.

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