Greater Perth in December 2021: very warm with an extreme heatwave in late December

December 2021 was very warm with mean maximum and minimum temperatures mostly a couple of degrees above average. An extreme heatwave occurred in late December, and Perth Metro recorded four consecutive days with temperature of 40 degrees starting on Christmas Day (25th)..

Light rainfall mid-month

  • Monthly rainfall totals were less than 10 mm for most sites, which were 10-50% of the December average, although it is typical in summer
  • Most sites recorded 2 to 3 days of light rainfall between the 17th and 19th from a weak cold front.

Well above average mean temperatures with an extreme heatwave in late December

  • Mean maximum temperatures were 1–3 °C above average across Greater Perth.
  • Perth Metro recorded a mean maximum temperature of 31.7 °C, which was 2.3 °C above average, the equal second-warmest December in Perth official records, equalling with 2020 and 1931 and behind the record of 33.1 °C in 2019.
  • Perth Airport recorded a mean maximum temperature of 32.5 °C, which was 3.3 °C above average, its second-warmest December on record, behind the record of 33.9 °C in 2019.
  • A severe to extreme heatwave hit Perth and surrounding areas in late December between the 24th and 29th, with maximum temperatures persisting over 40 °C and overnight temperatures remaining above 20 °C at many locations; a number of coastal sites had their highest December temperature on record on the 26th, and their warmest December night on record on the 27th.
  • Perth Metro recorded a total of 5 days with maximum temperature of at least 40 °C, which was the first time for any month. The previous highest count was a total of 4 days on several occasions in the Perth official records.
  • Four consecutive days with maximum temperature of at least 40 °C were recorded between the 25th and 28th, and it was the first such run for December and only the third occurrence for any month in the Perth official records. During this run, Perth Metro recorded its hottest Christmas Day (also the third-highest December temperature on the 25th) with 42.8 °C, and the second-highest December temperature on Boxing Day (26th) with 43.5 °C.
  • Perth Metro also had 6 consecutive days with maximum temperatures of 38 °C or above between the 24th and 29th, which was the first such run for December and the equal longest-run for any month in the Perth official records.

Perth Metro

  • Total rainfall for Perth Metro was 3.6 mm, which is 35% of the long-term average of 10.2 mm
  • The mean daily maximum temperature for Perth Metro was 31.7 °C, which is 2.3 °C above the long-term average of 29.4 °C
  • The warmest day was 43.5 °C on the 26th, and the coolest day was on the 17th when the temperature reached 22.7 °C
  • The mean daily minimum temperature for Perth Metro was 17.8 °C, which is 1.4 °C above the long-term average of 16.4 °C
  • The coldest morning was 11.2 °C on the 19th, and the warmest morning was on the 9th when the minimum temperature was 26.8 °C

Further information

Media
(03) 9669 4057

Extremes in December 2021
Hottest day 43.7 °C at Swanbourne on the 26th
Warmest days on average 33.7 °C at Pearce RAAF
Coolest days on average 26.6 °C at Rottnest Island
Coldest day 19.7 °C at Bickley on the 17th
Coldest night 8.1 °C at Karnet on the 19th
Coolest nights on average 14.5 °C at Karnet
Warmest nights on average 18.6 °C at Rottnest Island
Warmest night 28.0 °C at Pearce RAAF on the 26th
Warmest on average overall 25.0 °C at Pearce RAAF
Coolest on average overall 22.6 °C at Bickley
22.6 °C at Rottnest Island
Wettest overall 18.7 mm at Huntly
Wettest day 7.8 mm at Huntly on the 17th
Strongest wind gust 80 km/h at Pearce RAAF on the 7th

Record highest December temperature
New record
(°C)
Old
record
Years of
record
Average for
December
Rottnest Island 42.5 on the 26th 40.6 on the 6th in 1992 31 25.1
Swanbourne 43.7 on the 26th 43.0 on the 26th in 2007 29 28.0
Mandurah 41.0 on the 26th 40.1 on the 25th in 2010 21 27.3



Record highest December daily minimum temperature
New record
(°C)
Old
record
Years of
record
Average for
December
Pearce RAAF 28.0 on the 26th = 28.0 on the 20th in 2002 63 14.6
Karnet 24.6 on the 27th 23.6 on the 23rd in 2015 56 13.5
Rottnest Island 27.0 on the 27th 25.7 on the 17th in 1991 31 17.7
Swanbourne 27.2 on the 27th 25.9 on the 24th in 2002 29 16.7
Garden Island HSF 25.5 on the 27th 25.0 on the 24th in 2002 21 17.3



Summary statistics for December 2021
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean for
December
2021
Diff
from
average
Highest for
December
2021
Mean for
December
2021
Diff
from
average
Lowest for
December
2021
Total for
December
2021
Average
for
December
Rank of
December
2021
Fraction of
December
average
Bickley 30.2 +1.9 40.3 26th 15.0 +1.2 9.2 14th 6.0 14.3 average 42%
Garden Island HSF 27.1 +1.5 42.5 26th 18.2 +0.9 13.6 13th 2.2 9.5 low 23%
Jandakot Aero 31.6 +2.3 43.3 26th 16.8 +2.0 8.7 19th 2.6 10.3 average 25%
Karnet     40.0 27th 14.5 +1.0 8.1 19th 9.2 18.4 average 50%
Mandurah 29.5 +2.2 41.0 26th 18.2 +0.9 13.1 19th 1.4 14.5 low 10%
Millendon (Swan Valley) 32.9   42.9 26th 16.5   9.3 1st 5.8
Pearce RAAF 33.7 +3.2 43.3 25th 16.4 +1.8 8.8 20th 2.4 10.8 average 22%
Perth Airport 32.5 +3.3 43.3 26th 16.7 +1.7 9.0 20th 2.4 10.9 low 22%
Perth Metro 31.7 +2.3 43.5 26th 17.8 +1.4 11.2 19th 3.6 10.2 average 35%
Rottnest Island 26.6 +1.5 42.5 26th 18.6 +0.9 14.7 2nd 0.2 10.1 low 2%
Swanbourne 29.1 +1.1 43.7 26th 18.2 +1.5 12.7 1st 1.8 10.5 average 17%

Daily maximum temperatures for December 2021
12345678910111213141516171819202122232425262728293031
Bickley23.726.928.831.032.330.532.436.935.122.920.423.826.623.028.022.719.720.626.632.030.032.534.536.840.040.336.538.137.733.432.0
Garden Island HSF20.421.327.525.923.229.534.138.532.923.923.120.620.721.222.122.522.623.221.222.823.424.726.129.840.242.539.733.733.825.124.6
Gosnells City33.834.624.629.739.543.140.440.5
Jandakot Aero24.828.831.733.232.633.934.940.236.024.824.825.225.324.527.523.623.124.426.031.729.531.433.938.343.343.340.040.538.432.732.6
Karnet27.822.620.826.231.029.432.433.938.439.840.038.037.933.530.5
Mandurah22.726.430.431.230.032.434.438.529.724.823.923.824.423.524.622.922.922.423.427.327.529.130.837.941.041.040.234.933.230.829.8
Millendon (Swan Valley)25.829.131.333.434.833.235.439.536.925.625.626.529.425.531.125.723.324.928.734.531.933.837.240.042.642.941.540.940.134.834.5
Pearce RAAF26.630.031.734.335.833.736.039.938.025.726.626.730.326.731.826.224.325.729.235.632.935.137.941.143.343.242.042.140.835.135.2
Perth Airport26.028.931.533.533.833.435.139.936.825.025.126.128.025.429.724.423.424.327.132.931.732.536.039.743.143.340.641.539.534.233.7
Perth Metro24.526.431.333.132.333.435.240.035.225.025.225.327.024.328.324.222.724.526.131.829.931.034.938.642.843.541.040.738.633.132.1
Rottnest Island21.821.624.323.924.324.932.137.527.323.422.822.621.921.822.622.322.522.922.223.923.424.324.928.338.042.537.935.733.125.725.2
Swanbourne23.023.330.627.427.432.035.339.433.123.923.923.123.822.924.423.223.124.122.725.125.025.730.333.843.243.740.937.935.226.927.2
Values are the maximum temperature, usually in the 24 hours from 9 am on the day indicated,
and typically occurred in the afternoon of that day.
Temperatures coloured according to their difference
from the long-term average for the period
-10.0 -9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 +1.0 +2.0 +3.0 +4.0 +5.0 +6.0 +7.0 +8.0 +9.0 +10.0 °C Grey outline marks highest
and lowest for the period

Daily minimum temperatures for December 2021
12345678910111213141516171819202122232425262728293031
Bickley10.210.811.412.515.012.812.117.922.216.414.612.010.19.211.413.013.312.810.014.816.714.715.616.816.820.822.520.321.218.617.5
Garden Island HSF14.814.114.816.118.716.315.622.218.619.016.813.614.214.816.817.117.913.617.319.217.919.520.521.725.425.523.120.719.720.1
Gosnells City15.617.616.513.69.910.918.823.825.3
Jandakot Aero11.612.814.415.818.315.715.322.126.519.417.514.213.511.211.311.316.416.38.78.817.014.618.320.720.726.226.420.818.517.419.1
Karnet9.511.511.412.814.613.112.023.516.414.812.110.510.010.512.214.611.48.112.315.513.615.716.617.422.124.621.914.215.616.9
Mandurah13.614.014.716.119.016.315.521.520.919.418.816.113.613.214.116.817.317.713.115.918.617.819.520.021.325.426.824.923.819.918.8
Millendon (Swan Valley)9.313.215.216.218.616.015.822.325.819.813.312.411.810.510.511.713.813.210.79.415.013.717.821.420.925.727.225.317.817.718.1
Pearce RAAF9.912.715.016.217.916.315.922.725.919.412.710.913.110.610.910.712.813.29.48.813.913.318.421.521.728.027.425.617.417.617.1
Perth Airport11.914.114.916.018.516.315.521.626.719.616.614.612.511.312.611.312.914.09.19.016.113.818.920.520.524.526.323.918.417.718.6
Perth Metro13.014.315.116.318.916.615.721.826.819.618.015.813.813.313.513.816.715.211.212.218.217.519.419.820.826.025.822.220.219.320.9
Rottnest Island15.514.715.316.619.316.815.821.420.718.717.417.014.715.215.317.516.216.514.817.718.818.420.120.922.124.927.024.221.920.020.1
Swanbourne12.713.615.116.618.216.215.922.724.519.118.215.614.213.313.314.716.717.313.114.018.517.418.821.121.925.927.225.322.419.220.9
Values are the minimum temperature, usually in the 24 hours to 9 am on the day indicated,
and typically occurred that morning.
Temperatures coloured according to their difference
from the long-term average for the period
-10.0 -9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 +1.0 +2.0 +3.0 +4.0 +5.0 +6.0 +7.0 +8.0 +9.0 +10.0 °C Grey outline marks highest
and lowest for the period

Daily rainfall for December 2021
12345678910111213141516171819202122232425262728293031
Anketell - - - - - - - - - - - - - - - - 2.6 - 1.4 - - - - - - - - - - - -
Bickley - - - - - - - - - - 0.4 - - - - - 4.2 0.2 1.2 - - - - - - - - - - - -
Bungendore - - - - - - - - - - - - - - - - 3.8 0.4 2.4 - - 0.4 - - - - - - - - -
Chidlow - - - - - - - - - - 0.1 - - - - - 5.3 1.0












Garden Island HSF - - - - - - - - -
- - - - - - 1.4
0.8 - - - - - - - - - - - -
Gidgegannup - - - - - - - - - - - - - - - - 6.4 0.8 0.2 - - - - - - - - - - - -
Gosnells City


- -




- - 0.6 - - - - - - - -
- - - -
Huntly - - - - - - - - - - 1.0 0.9 - - - 1.0 7.8 1.0 7.0 - - - - - - - - - - - -
Jandakot Aero - - - - - - - - 0.6 - - - - - - - 1.8 - - - - 0.2 - - - - - - - - -
Jarrahdale - - - - - - - - - - 0.4 - - - - - 2.0 0.2 2.8 - - - - - - - - - - - -
Karnet - - - - - - - - - - - - - - - - 4.6 0.6 4.0 - - - - - - - - - - - -
Karragullen North - - - - - - - - - - - - - - - - 6.6 0.5 0.6











Maida Vale - - - - - - - - - - - - - - - - 1.6













Mandurah - - - - - - - - - - - - - - - - 0.6 0.2 0.6 - - - - - - - - - - - -
Millendon (Swan Valley) - - - - - - - - - - - - - - - - 5.4 0.4 - - - - - - - - - - - - -
Mount Solus - - - - - - - - - - 0.4 0.2 - - - - 3.8 0.8 2.0 - - - - - - - - - - - -
Muchea - - - - - - - - - - - - - - - - 1.2 - 0.2 - - - - - - - - - - - -
Mundaring - - - - - - - - - - - - - - - - 4.8 0.4 1.0











Pearce RAAF - - - - - - - - - - - - - - - - 1.0 1.4 - - - - - - - - - - - - -
Perth Airport - - - - - - - - - - - - - - - - 2.2 0.2 - - - - - - - - - - - - -
Perth Metro - - - - - - - - - - - - - - - - 3.2 - 0.4 - - - - - - - - - - - -
Pinjarra Refinery - - - - - - - - - - 0.8 - - - - - 3.4 0.1 3.2 - - - - - - - - - - - -
Pinjarra South - - - - - - - - - - - - - - - - 3.2 - 1.4 0.2 - - - - - - - - - - -
Roleystone - - - - - - - - - - - - - - - - 4.0













Rottnest Island - - - - - - - - - - - - - - - - 0.2 - - - - - - - - - - - - - -
Serpentine - - - - - - - - - - - - - - - - 1.2 0.2 0.2 - - - - - - - - - - - -
Subiaco Treatment Plant - - - - - -
























Swanbourne - - - - - - - - - - - - - - - - 0.6 - 0.6 - - 0.6 - - - - - - - - -
Tamala Park (Mindarie) - - - - - - - - - - - - - - - -














Wanneroo - - - - - - - - - - - - - - - - 2.2













Werribee - - - - - - - - - - - - - - - - 3.2 1.0 - - - - - - - - - - - - -
Whiteman Park - - - - - - - - - - - - - - - - 3.8 - - 0.8 - - - - - - - - - - -
Most values are the precipitation in the 24 hours to 9 am on the day indicated. Days marked with → are part of a longer accumulation, which is shown on the final day.
Values over 100 mm have been rounded to the nearest whole millimetre.
Days marked with - have a rainfall report of zero; days left blank have no rainfall report (which often indicates no rain fell).
Rainfalls coloured
according to the amount
0 1.0 5.0 10.0 15.0 25.0 50.0 100 150 200 300 400 600 millimetres

Notes

The Monthly climate summary, generally published on the first working day of each month, 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 3 pm on Tuesday 4 January 2022. 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