Perth in December 2012: A very wet and hot month

  • Rainfall: above average; wettest on record at some sites
  • Maximum temperature: Above average; 3rd hottest December for Perth Metro
  • Minimum temperature: Above average

Rainfall

Rainfall across the Perth metropolitan area during December 2012 was very much above average, with monthly rainfall totals generally ranging from 20 mm to 50 mm as thunderstorms during the first half of the month brought some significant falls. Medina Research Centre and Garden Island experienced their wettest December in 29 years and 11 years respectively.

A surface trough combined with a middle level disturbance to produce showers and thunderstorms in the Perth metropolitan area in the early morning on the 5th, with further showers on the 6th, followed by a weak cold front that moved through the Perth region on the 7th. Typically light rainfall was observed during these events with falls mostly below 5 mm. A significant rainfall event for the Perth region occurred on the 12th, when a deep surface trough interacted with a slow moving middle level low off the west coast. Thunderstorms with moderate to heavy rainfall were observed during the event across most metropolitan sites. Champion Lakes, near Armadale in the southeast suburbs, received a daily rainfall of 50.6 mm on the 13th, the highest daily total in December in the Perth area. Medina Research Centre (30 years of record), Swanbourne (20 years), and Garden Island (12 years) all recorded their wettest December day on the 12th.

Perth Metro recorded 20.2 mm of rainfall on 6 rain days in December 2012, above the long-term December average of 13.3 mm. The highest daily fall at Perth Metro during December 2012 was 8.6 mm on the 12th. Historically, December rainfall in Perth has ranged from 0.0 mm on 6 occasions to 80.7 mm in 1951, while last December (2011), Perth Metro recorded 75.8 mm on 3 rain days, the third wettest December since records commenced in 1876.

Maximum temperature

Mean maximum temperatures in December 2012 across the Perth metropolitan area were above to very much above average, mainly due to a very hot end to the month. Mean maxima were in the high twenties to low thirties.

December 2012 started with a cool to mild day with southerly winds over the metropolitan area and some coastal sites recorded their lowest maximum temperature for the month. This was followed by warm to hot days 3rd and the 4th. Temperatures on the 4th were in the high thirties at most sites. Mostly mild to warm days were reported from the 5th to the 20th, although warm to hot days were reported on the 9th and 10th. With the exception of the island sites, Perth experienced a prolonged heatwave (three or more consecutive days with maximum temperatures of 35 °C or higher) commencing on Christmas day and culminating in the hottest conditions on New Years Eve. Most sites saw a run of seven consecutive very hot days with maximum temperatures in excess of 37 °C from the 25th to 31st, with 31st the hottest day of the month across the Perth area when daily maxima exceeded 40 °C for most sites and Gosnells City observed the highest temperature of 43.0 °C. The seven consecutive days of maximum temperature of 37 °C or more at Perth Metro has only been matched on two previous occasions (31 December to 6 January 1962 and 15 to 21 February 1988); while Perth Metro's longest heatwave of 35 °C or more was ten days set on two occasions (12 to 21 February 1975 and 12 to 21 February 1988).

Perth Metro's mean daily maximum temperature in December was 31.2 °C, which was the third warmest December on record since records commenced in 1897 and the warmest since the 31.4 °C in December 1999. Daily maxima at Perth Metro ranged from a very hot 42.1 °C on the 31st, which was the hottest day in December at Perth Metro since 44.2 °C on 26 December 2007 (the hottest December day on record), to a mild 23.6 °C on the 7th.

Minimum temperature

Mean minimum temperatures in December 2012 were above to very much above average across the Perth metropolitan area, with mean minima generally in mid to high teens. Bickley observed a mean minimum temperature of 15.4 °C, their warmest December in terms of minimum temperature in 18 years of record.

The first day of December 2012 saw cool overnight temperatures across the Perth area, with minima generally 6 °C to 9 °C cooler than normal. A minimum of 6.2 °C at Perth Airport on the 1st was the lowest temperature recorded for the month for the Perth area. Another cool night was experienced on the 8th, with daily minima below 10 °C for most sites on the coastal plain and in the hills. All metropolitan sites reported their coolest morning of the month either the 1st or 8th. Complimenting the very hot daytime temperatures, warm to hot nights were experienced from the 25th to 31st, with daily minima remaining in twenties for most sites. The 29th was the hottest night of the month across the Perth area, and the daily minimum temperature of 28.0 °C at Gosnells City was not only the highest overnight temperature of the month for Perth area, but also their highest overnight temperature in December in 21 years of record. Perth Metro, Perth Airport and Jandakot Aero also observed their highest December minimmum temperature on record on the 29th.

Perth Metro's mean daily minimum temperature in December 2012 was 17.8 °C, which was well above the long-term mean of 16.3 °C. Daily minima ranged from a cool 9.4 °C on the 8th to a record hot 27.3 °C on the 29th.

Sunshine

The mean daily sunshine hours for December was 10.8 hours, which is 0.7 hours below average of 11.5 hours.

Further information

Media
(03) 9669 4057
Enquiries

Extremes in December 2012
Hottest day 43.0 °C at Gosnells City on the 31st
Warmest days on average 32.7 °C at Pearce RAAF
Coolest days on average 26.8 °C at Rottnest Island
Coldest day 19.7 °C at Bickley on the 7th
Coldest night 6.2 °C at Perth Airport on the 1st
Coolest nights on average 15.4 °C at Bickley
Warmest nights on average 18.8 °C at Rottnest Island
Warmest night 28.1 °C at Champion Lakes on the 29th
Wettest overall 75.6 mm at Champion Lakes
Driest overall 20.2 mm at Perth Metro
Wettest day 50.6 mm at Champion Lakes on the 13th
Highest wind gust 74 km/h at Champion Lakes on the 26th

Record highest December daily rainfall
Highest daily rainfall
in December 2012 (mm)
Previous wettest
for December
Years of
record
Medina Research Centre 35.6 on the 12th 26.8 on the 13th in 2011 30
Swanbourne 30.2 on the 12th 29.8 on the 13th in 2011 20
Garden Island HSF 38.6 on the 12th 19.4 on the 7th in 2011 12



Record highest total December rainfall
Total rainfall
for December 2012 (mm)
Previous wettest
for December
Years of
record
Average for
December
Medina Research Centre 56.2 51.8 in 2011 30 12.1
Garden Island HSF 52.0 38.8 in 2011 12 13.3




Record highest December daily minimum temperature
Highest daily minimum
temperature
in December 2012 (°C)
Previous warmest
for December
Years of
record
Average for
December
Perth Airport 27.5 on the 29th 26.9 on the 24th in 1960 69 14.9
Jandakot Aero 27.6 on the 29th 25.9 on the 27th in 2003 23 14.6
Gosnells City 28.0 on the 29th 27.3 on the 23rd in 1997 21 16.1
Perth Metro 27.3 on the 29th 27.1 on the 18th in 1979 114 16.3



Record highest December mean daily minimum temperature
Mean daily minimum
temperature
for December 2012 (°C)
Previous warmest
for December
Years of
record
Average for
December
Bickley 15.4 15.2 in 2011 18 13.5



Summary statistics for December 2012
Maximum temperatures
for December
(°C)
Minimum temperatures
for December
(°C)
Rainfall
for December
(millimetres)
Mean for
December
2012
Diff
from
average
Highest for
December
2012
Mean for
December
2012
Diff
from
average
Lowest for
December
2012
Total for
December
2012
Average
for
December
Rank of
December
2012
Fraction of
December
average
Bickley 29.2 +1.3 38.6 31st 15.4 +1.9 8.2 1st 36.2 13.8 high 262%
Champion Lakes 30.6   40.8 31st 18.1   9.6 1st 75.6
Garden Island HSF 27.0 +1.6 36.6 30th 18.5 +1.4 13.2 1st 52.0 13.3 highest 391%
Gosnells City 32.3 +2.0 43.0 31st         25.4 11.7 high 217%
Jandakot Aero 30.7 +1.8 41.2 31st 16.4 +1.8 6.6 8th 28.8 11.0 v high 262%
Pearce RAAF 32.7 +2.5 42.7 31st 16.4 +1.9 6.7 1st 42.8 10.8 v high 396%
Perth Airport 31.4 +2.5 42.2 31st 16.8 +1.9 6.2 1st 22.8 11.4 high 200%
Perth Metro* 31.2 +2.3 42.1 31st 17.8 +1.5 9.4 8th 20.2 13.3 v high 151%
Rottnest Island 26.8 +1.8 37.5 31st 18.8 +1.3 14.4 1st 27.6 8.2 v high 337%
Swanbourne 30.0 +2.2 40.6 31st 17.9 +1.4 11.4 8th 52.2 12.9 v high 405%

Daily maximum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley22.726.630.034.123.521.319.725.931.833.028.024.221.425.326.329.223.722.429.032.730.325.725.731.937.137.835.536.838.635.238.6
Champion Lakes24.129.232.336.924.423.022.328.534.034.229.124.824.926.527.429.824.424.529.634.630.026.526.233.438.139.538.037.839.236.040.8
Garden Island HSF21.524.231.735.323.122.522.023.830.630.825.922.725.721.622.423.922.223.026.030.822.822.124.929.735.629.731.128.633.336.631.5
Gosnells City25.530.032.837.726.724.923.529.535.335.831.025.726.028.029.031.625.830.635.932.528.534.039.539.240.042.538.743.0
Jandakot Aero23.729.633.437.024.023.723.028.134.533.529.224.226.026.027.130.124.125.028.134.229.826.626.332.338.839.837.638.339.637.541.2
Medina Research Centre23.129.333.537.824.224.423.534.134.030.024.526.531.1
Pearce RAAF25.930.934.337.528.126.425.630.036.035.932.425.625.227.930.833.726.426.731.636.331.628.928.335.140.242.038.538.142.139.442.7
Perth Airport24.529.833.637.025.924.023.428.935.035.730.625.125.126.628.331.525.026.029.535.030.727.027.133.138.940.537.838.140.438.242.2
Perth Metro24.429.833.738.224.724.123.628.135.134.130.124.725.526.028.331.424.725.128.435.329.826.726.732.739.637.538.339.340.537.542.1
Rottnest Island21.123.727.136.122.423.222.722.429.131.324.722.223.923.023.124.223.422.823.630.224.124.123.928.435.927.030.431.532.534.337.5
Swanbourne24.230.135.037.922.724.323.825.835.631.327.023.627.225.026.728.024.725.027.135.826.225.426.031.738.931.437.537.537.336.340.6

This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.
The temperatures in this table are coloured by
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 difference from average


Daily minimum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley8.210.712.414.118.316.414.49.211.418.517.413.515.213.512.513.913.914.310.713.018.314.214.514.318.021.116.623.123.521.721.7
Champion Lakes9.614.516.518.320.318.816.410.415.421.221.815.816.717.314.916.614.417.613.017.317.315.316.517.921.522.620.424.928.126.523.6
Garden Island HSF13.214.916.519.020.219.517.613.915.818.316.616.917.918.216.017.017.619.314.817.720.418.219.418.220.421.920.423.624.523.421.9
Gosnells City10.114.816.519.017.310.519.021.215.517.814.914.516.513.817.216.916.714.516.020.522.025.528.026.523.2
Jandakot Aero7.113.416.218.119.819.216.46.613.118.115.815.317.814.912.314.813.117.811.716.215.213.414.316.417.720.220.123.427.622.219.9
Medina Research Centre10.014.315.718.419.419.316.99.018.416.515.217.515.313.418.3
Pearce RAAF6.712.316.419.819.718.516.27.814.819.916.316.717.315.914.014.013.115.212.214.214.111.614.316.918.517.320.624.927.522.719.8
Perth Airport6.212.716.018.219.518.517.17.513.520.418.516.117.615.815.214.611.818.012.716.015.215.214.016.418.122.820.123.827.520.820.9
Perth Metro10.015.116.618.620.019.017.89.415.219.418.316.617.817.115.015.715.618.613.817.119.215.917.017.319.023.020.224.327.321.520.9
Rottnest Island14.415.317.119.120.618.916.315.016.420.019.815.815.718.316.718.018.318.616.118.620.118.418.618.620.820.920.723.224.124.223.6
Swanbourne12.214.316.519.219.019.317.311.415.520.818.315.616.616.314.915.116.118.412.917.518.515.217.216.820.321.820.624.924.225.823.3

This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.
The temperatures in this table are coloured by
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 difference from average


Daily rainfall
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley - - - - 1.2 3.0 3.2 - - - 1.6 0.4 23.2 3.4 - - - 0.2 - - - - - - - - - - - - -
Champion Lakes - - - - 1.4 2.8 1.8 0.6 - - - 18.4 50.6 - - - - - - - - - - - - - - - - - -
Garden Island HSF - - - - 2.0 3.0 1.4 - - - - 38.6 7.0 - - - - - - - - - - - - - - - - - -
Gosnells City - - - »» »» 1.4 1.6 - - - 0.8 6.4 14.4 0.8 - - - - - - - - -
- - - - - - -
Jandakot Aero - - - - 4.6 1.4 2.2 0.2 - - - 6.2 14.2 - - - - - - - - - - - - - - - - - -
Jarrahdale - - - 0.6 1.4 1.6 6.6 0.2 - - - 11.8 0.4 0.2 - 0.2 - - 0.6 - - - - - - - - - - - -
Medina Research Centre - - - - 6.2 1.6 1.2 0.4 - - - 35.6 11.2 - - - - -












Pearce RAAF - - - - 0.4 0.8 1.2 - - - 8.0 1.0 28.2 3.2 - - - - - - - - - - - - - - - - -
Perth Airport - - - - 1.6 2.0 0.8 0.2 - - 0.4 3.0 14.0 0.8 - - - - - - - - - - - - - - - - -
Perth Metro - - - - 2.6 2.0 1.0 - - - 0.8 8.6 5.2 - - - - - - - - - - - - - - - - - -
Roleystone - - - - 0.2 2.6 4.4 - - 0.2 0.2 6.6 9.6 0.4 - - - 0.4
Rottnest Island - - - - 0.2 2.6 0.8 - - - 0.2 13.6 10.0 - - - - - 0.2 - - - - - - - - - - - -
Serpentine - - - - 4.2 1.4 2.4 - - - 0.4 42.8 0.6 - - - - - 0.2 - - - - - - - - - - - -
Swanbourne - - - - 3.8 1.0 0.4 - - - 0.8 30.2 16.0 - - - - - - - - - - - - - - - - - -

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 marked like this 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).
This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.


Notes

A Monthly Climate Summary is prepared to list the main features of the weather in Perth using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at 9 am on Wednesday 2 January 2013. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

Averages 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.
The median is sometimes more representative than the mean of long-term average rain.

*Official Perth observations have been recorded at several different sites with varying instrumentation over the years, and these changes can affect the continuity of the climate record. For the current Mt Lawley site, the most significant changes of this kind relate to minimum temperature and rain days.

For that reason, current mean temperature and rain-day data quoted here are based only on readings from the Mt Lawley site, which commenced observations in 1993. Sunshine recordings are from Perth Airport and for similar reasons current means use only Perth Airport data, which commenced in 1993.

For PDF files of Perth Metro climate statistics for other months, please click here for extremes and here for averages.

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.

Further information

Media
(03) 9669 4057
Enquiries