Greater Perth in 2020: A mild start with hot finish, dry winter

Annual rainfall in 2020 at Perth Metro was below average, an accumulation of its fourth-driest winter on record, third-driest October on record but a record wet November. Bickley was the only site in Greater Perth that recorded above average annual rainfall. Daytime temperatures and night-time temperatures were above average for most sites.

Below average annual rainfall for most sites

  • Annual rainfall was below average for most sites, except for Bickley, with annual rainfall totals in the 450–700 mm range, up to 1000–1200 mm in the Perth hills.
  • Rainfall in November was more than double the November average across Greater Perth and most sites had their wettest November on record
  • Perth Metro's monthly rainfall of 92 mm in November was also the highest November rainfall for any central Perth sites with observations dating back to 1867.
  • A number of cold fronts produced 4 consecutive wet days at the end of June; Bickley recorded 90.2 mm on the 29th, which was its second highest June daily rainfall on record and the highest daily rainfall of 2020 in Greater Perth.

Above average daytime and night-time temperatures

  • Mean maximum and minimum temperatures for 2020 were mostly less than 1 °C of above average.
  • The hottest day of 2020 was 4 February with temperatures reaching the low-to-mid 40s for most sites; Pearce RAAF's 44.6 °C was the highest temperature of 2020.
  • The coldest day was 3 August with temperatures in the low-10s for most sites; Swanbourne's maximum temperature of 11.6 °C was its coldest day for any month on record.

Perth Metro

  • Total rainfall for Perth Metro was 673.4 mm, which is 92% of the long-term average of 730.9 mm
  • The mean daily maximum temperature for Perth Metro was 25.3 °C, which is 0.5 °C above the long-term average of 24.8 °C
  • The warmest day was 42.7 °C on 4 February, and the coolest day was on 3 August when the temperature reached 12.1 °C
  • The mean daily minimum temperature for Perth Metro was 13.5 °C, which is 0.7 °C above the long-term average of 12.8 °C
  • The coldest morning was 3.4 °C on 20 June, and the warmest morning was on 20 February when the minimum temperature was 24.6 °C

Highest wind gust for over a decade at Rottnest Island

  • Rottnest Island recorded the highest gust at 113 km/h (61 knots) on 5 May, its highest wind gust in May since 115 km/h (62 knots) on 21 May 2009.
  • A strong and complex weather system in May

  • Ex-TC Mangga, combined with an upper level trough and strong cold front, followed by a deep low to produce widespread severe weather over western parts of WA, including Perth on 24 and 26 May.
  • Widespread moderate rainfall and damaging winds, locally destructive gusts, and abnormally high tides were recorded during the event.
  • In Rockingham, coastal erosion washed away a cycle path on the foreshore. The tide gauge at Barrack Street peaked at 1.88m and flooding was reported on Mounts Bay Road, Riverside Drive and Barrack Street. Other riverside cycleways and footpaths were inundated.
  • Further information

    Media
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    Extremes in 2020
    Hottest day 44.6 °C at Pearce RAAF on 4 Feb
    Warmest days on average 26.3 °C at Pearce RAAF
    Coolest days on average 22.7 °C at Rottnest Island
    Coldest day 10.4 °C at Bickley on 3 Aug
    Coldest night 1.7 °C at Jandakot Aero on 19 May
    1.7 °C at Pearce RAAF on 21 May
    Coolest nights on average 11.2 °C at Karnet
    Warmest nights on average 16.1 °C at Rottnest Island
    Warmest night 26.2 °C at Gosnells City on 30 Dec
    26.2 °C at Pearce RAAF on 30 Dec
    Warmest on average overall 19.7 °C at Pearce RAAF
    Coolest on average overall 17.2 °C at Bickley
    Wettest overall 1161.2 mm at Bickley
    Driest overall 453.4 mm at Rottnest Island
    Wettest day 90.2 mm at Bickley on 29 Jun
    Strongest wind gust 113 km/h at Rottnest Island on 5 May

    Record lowest daily maximum temperature
    New record
    (°C)
    Old
    record
    Years of
    record
    Annual
    average
    Swanbourne 11.6 on 3 Aug 12.2 on 26 Jul 1998 28 24.1



    Summary statistics for 2020
    Maximum temperatures
    (°C)
    Minimum temperatures
    (°C)
    Rainfall
    (millimetres)
    Mean
    for
    2020
    Diff
    from
    average
    Highest
    for
    2020
    Mean
    for
    2020
    Diff
    from
    average
    Lowest
    for
    2020
    Total
    for
    2020
    Average
    annual
    total
    Rank
    of
    2020
    Fraction
    of annual
    average
    Bickley 22.8 +0.2 39.5 4 Feb 11.7 +0.4 3.8 20 Jun 1161.2 1082.1 average 107%
    Garden Island HSF 23.1 +0.4 40.3 4 Feb 15.4 +0.4 5.0 31 Aug
    Jandakot Aero 25.1 +0.5 41.6 4 Feb 12.7 +1.2 1.7 19 May 664.8 816.0 low 81%
    Karnet 22.9 +0.3 39.2 27 Jan 11.2 +0.6 2.8 19 Aug 1014.0 1150.4 low 88%
    Millendon (Swan Valley) 26.0   43.6 4 Feb 12.6   2.8 21 May 610.6
    Pearce RAAF 26.3 +1.0 44.6 4 Feb 13.0 +0.8 1.7 21 May
    Perth Airport 25.7 +1.2 43.3 4 Feb 12.9 +0.7 2.3 19 May 636.6 760.4 low 84%
    Perth Metro 25.3 +0.5 42.7 4 Feb 13.5 +0.7 3.4 20 Jun 673.4 730.9 low 92%
    Rottnest Island 22.7 +0.5 38.6 4 Feb 16.1 +0.4 7.7 3 Oct 453.4 563.9 v low 80%
    Swanbourne 24.0 -0.1 42.1 4 Feb 14.8 +0.8 6.1 20 Jun

    Notes

    The Annual climate summary, generally published on the second working day of the year, lists the main features of the weather in Greater Perth using the most timely and accurate information available on the date of publication; it will generally not be updated. More extensive discussion of significant weather events, along with later information and data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review.

    This summary includes data from observing sites in or near the Greater Perth “Greater Capital City Statistical Area” (GCCSA). The Australian Bureau of Statistics designed the GCCSAs to “include the population within the urban area of the city, as well as people who regularly socialise, shop or work within the city, and live in small towns and rural areas surrounding the city. It is important to note that GCCSAs do not define the built up edge of the city. They provide a stable definition for these cities and are designed for the output of a range of social and economic survey data.

    This statement has been prepared based on information available at 7 am on Monday 4 January 2021. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

    In some situations, some or all of the rainfall is in the form of hail or snow. In these cases the totals given are for the water equivalent: the depth of liquid water that results from melting any frozen precipitation. There can be significant 'undercatch' of snow in strong winds, meaning the true precipitation can be higher than that reported.

    Averages for individual sites are long-term means based on observations from all available years of record, which vary widely from site to site. They are not shown for sites with less than 10 years of record, as they cannot then be calculated reliably.
    The median is sometimes more representative than the mean of long-term average rain.

    The Rank indicates how rainfall this time compares with the climate record for the site, based on the decile ranking (very low rainfall is in decile 1, low in decile 2 or 3, average in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
    The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.

    Where temperature area averages are mentioned, they are derived from the ACORN-SAT dataset.

    Further information

    Media
    (03) 9669 4057

    Climate