Perth in January 2012: A very hot January

This statement was prepared before all data for the period were available. This may affect some of the statistics presented.

  • Rainfall: Mostly average to above average
  • Maximum temperature: Above average for most sites
  • Minimum temperature: Highest on record for most sites

Rainfall

Rainfall across the Perth metropolitan area during January 2012 ranged from near average in western suburbs to above average in southern and eastern suburbs. Rainfall totals varied from less than 5 mm in coastal suburbs and on Rottnest Island to above 80 mm in the hills. The higher totals were mainly the result of one significant thunderstorm event in the second half of the month, which caused record January daily falls at several sites.

Overnight thunderstorms on the 3rd produced generally light rainfall across the Perth metropolitan area, with daily falls of less than 10 mm registered on the 4th. This was the first rainfall in Perth for three weeks since 13 December 2011. Further light showers occurred in the eastern suburbs and hills in the evening of the 5th and in the morning of the 6th, with daily totals less than 5 mm. After a length dry period, a surface trough off the west coast produced slow moving thunderstorms with significant rainfall across the Perth metropolitan area in the evening of the 19th and in the morning of the 20th. Rainfall totals during the event were generally in the 10 mm to 70 mm range. As a result, Jarrahdale, Mundaring and Chidlow registered their wettest January day in more than 100 years of rainfall record. Serpentine also witnessed its highest daily rainfall for January, and as a result of this single event recorded its wettest January in 86 years of record. Thunderstorms brought rain to most sites in the Perth metropolitan area on the afternoon and evening of Australia day, the 26th, though falls were generally less than 5 mm.

Perth Metro observed 18.8 mm on 5 rain days in January 2012, which was well above the long-term average of 9.6 mm. Last January, Perth Metro recorded 30.2 mm on 6 rain days.

Across December 2011 and January 2012, Perth Metro recorded 94.6 mm on 8 rain days, which is the 4th wettest December to January period since records commenced in 1876, and the wettest start to summer in 12 years, since 146.2 mm was recorded on 13 rain days in December 1999 and January 2000.

Maximum temperature

Although mean maxima at Pearce RAAF in the north and Bickley in the hills were close to average, most sites in the Perth metropolitan area saw above to very much above average mean maxima, in the range of 1.1 °C to 3.5 °C above normal. Swanbourne recorded its hottest January in 18 years of recording, whilst Garden Island also saw a record, though with only 10 years of recording history.

Cooler than normal days were experienced on the first day of January 2012, and between the 5th and the 8th, with daily maxima mostly in the mid-to-high twenties. In contrast, from the 10th of the month, a number of hot spells were experienced. The first heatwave (three or more consecutive days with maximum temperatures of 35 °C or higher) was mostly confined to the southeast and western suburbs between the 11th and 13th, whilst a second 4-day heatwave was witnessed at Perth Metro, Perth Airport, and Jandakot Aerodrome between the 18th and the 21st. Most sites in the Perth area experienced a very hot spell during the period between the 24th and the 28th, with daily maxima in the 35 to 43 °C range. The hottest day of the month was Australia day (26th) for most sites, though the 25th or 28th was hotter for some metropolitan locations, and the 43.1 °C on the 26th at Swanbourne was the highest temperature recorded in the Perth metropolitan area for the month, and also the highest temperature recorded at Swanbourne in 19 years of record. Cooler air from the southeast with maxima mostly in the low thirties brought some relief in the last days of the month after some sites recorded a six day heatwave.

Perth Metro's mean daily maximum temperature in January 2012 was 33.5 °C, which was 2.6 °C above the January average and the second hottest January on record, only behind the mean maximum of 34.4 °C recorded in January 1962. Daily maxima in January 2012 ranged from a mild 24.6 °C on the 7th, to a very hot 42.1 °C on the 28th.

Minimum temperature

Mean minimum temperatures in January 2012 were very much above average across the Perth region. Most sites observed their warmest January on record due to a large number of warm to very warm nights in the middle and latter parts of the month. Perth Airport recorded its warmest January in 67 years of record, whilst Rottnest Island recorded its 2nd warmest January from records going back to 1880, and its warmest January since the record was set in 1934. Mean overnight temperatures were generally in the 19 °C to 21 °C range across the city.

Warm nights (when the daily minimum temperature is 20 °C or higher) were experienced at many sites between the 13th and 14th, 19th and 22nd, and 24th and 29th. The hottest night of the month was the 28th with daily minima mostly in the 26 °C to 28 °C range as a number of sites recorded their hottest January night on record, and Gosnells City recorded the highest minimum for the month in Perth with 29.0 °C. The minimum temperature of 26.4 °C at Rottnest Island is the third highest minimum temperature recorded on the island since daily records commenced 1965.

Perth Metro's mean daily minimum temperature in January 2012 was 20.1 °C, which is 2.2°C above the average, and the warmest January for 20 years since a mean minimum of 20.6 °C was recorded in 1992. Daily minima ranged from a mild 13.5 °C on the 8th to a very warm 26.6 °C on the 28th. Last January, Perth Metro recorded a mean minimum temperature of 19.5 °C.

Wind and Sunshine

The highest wind gust recorded in the Perth metropolitan area in January was 98 km/h at Bickley on the 30th.

Perth recorded an average daily sunshine of 11.3 hours per day in January 2012, which is slightly below the average of 11.6 hours.

Further information

Media
(03) 9669 4057
Enquiries

Extremes in January 2012
Hottest day 43.1 °C at Swanbourne on the 26th
Warmest days on average 34.2 °C at Gosnells City
Coolest days on average 29.6 °C at Rottnest Island
30.5 °C at Bickley
Coldest day 22.0 °C at Garden Island HSF on the 7th
22.3 °C at Bickley on the 6th
Coldest night 9.8 °C at Jandakot Aero on the 8th
Coolest nights on average 16.9 °C at Bickley
Warmest nights on average 20.8 °C at Rottnest Island
20.6 °C at Gosnells City
Warmest night 29.0 °C at Gosnells City on the 28th
Warmest on average overall 27.5 °C at Gosnells City
Coolest on average overall 23.7 °C at Bickley
Wettest overall 100.2 mm at Chidlow
Wettest day 86.4 mm at Chidlow on the 20th
Highest wind gust 98 km/h at Bickley on the 30th

Record highest January daily rainfall
Highest daily rainfall
in January 2012 (mm)
Previous wettest
for January
Years of
record
Jarrahdale 60.6 on the 20th 58.2 on the 21st in 1982 105
Mundaring 68.8 on the 20th 36.8 on the 20th in 1923 104
Chidlow 86.4 on the 20th 64.3 on the 21st in 1957 104
Serpentine 60.6 on the 20th 27.9 on the 1st in 1960 86



Record highest total January rainfall
Total rainfall
for January 2012 (mm)
Previous wettest
for January
Years of
record
Average for
January
Serpentine 60.6 44.9 in 1960 89 9.6




Record highest January temperature
Highest temperature
in January 2012 (°C)
Previous warmest
for January
Years of
record
Average for
January
Swanbourne 43.1 on the 26th 42.9 on the 17th in 2010 19 29.5



Record highest January mean daily maximum temperature
Mean daily maximum
temperature
for January 2012 (°C)
Previous warmest
for January
Years of
record
Average for
January
Swanbourne 33.0 32.0 in 2010 18 29.5
Garden Island HSF 30.4 28.9 in 2010 10 27.0



Record highest January daily minimum temperature
Highest daily minimum
temperature
in January 2012 (°C)
Previous warmest
for January
Years of
record
Average for
January
Jandakot Aero 27.3 on the 28th 27.1 on the 19th in 2010 22 16.6
Gosnells City 29.0 on the 28th 28.6 on the 19th in 2010 19 18.4
Swanbourne 28.0 on the 28th 26.5 on the 7th in 1998 19 18.0
Garden Island HSF 25.9 on the 28th 24.4 on the 19th in 2010 11 18.7



Record highest January mean daily minimum temperature
Mean daily minimum
temperature
for January 2012 (°C)
Previous warmest
for January
Years of
record
Average for
January
Perth Airport 19.7 19.5 in 1962 67 17.0
Pearce RAAF 20.0 19.8 in 1989 50 16.9
Medina Research Centre 19.8 18.8 in 2011 23 16.8
Jandakot Aero 19.4 18.8 in 1992 21 16.6
Bickley 16.9 16.8 in 2011 18 15.2
Gosnells City 20.6 20.5 in 2011 18 18.4
Swanbourne 20.4 19.3 in 2011 18 18.0
Garden Island HSF 20.4 19.9 in 2011 10 18.7



Summary statistics for January 2012
Maximum temperatures
for January
(°C)
Minimum temperatures
for January
(°C)
Rainfall
for January
(millimetres)
Mean for
January
2012
Diff
from
average
Highest for
January
2012
Mean for
January
2012
Diff
from
average
Lowest for
January
2012
Total for
January
2012
Average
for
January
Rank of
January
2012
Fraction of
January
average
Bickley 30.5 -0.1 38.0 26th 16.9 +1.7 10.6 8th 52.8 18.1 v high 292%
Champion Lakes 32.5   40.6 28th 20.3   12.1 8th 21.6
Garden Island HSF 30.4 +3.4 40.2 25th 20.4 +1.7 15.0 8th 24.6 11.6 high 212%
Gosnells City 34.2 +1.1 42.5 28th 20.7 +2.3 11.0 8th 14.8 12.0 high 123%
Jandakot Aero 33.4 +2.2 41.5 26th 19.4 +2.8 9.8 8th 12.8 14.6 high 88%
Medina Research Centre 33.1 +2.6 41.8 26th 19.8 +3.0 10.6 8th 35.2 12.2 high 289%
Pearce RAAF 33.9 +0.4 41.3 26th 19.8 +2.9 10.9 8th        
Perth Airport 33.4 +1.7 41.5 26th 19.7 +2.7 11.9 8th 27.2 9.7 v high 280%
Perth Metro 33.5 +2.6 42.1 28th 20.1 +2.2 13.5 8th 18.8 9.6 high 196%
Rottnest Island 29.6 +3.3 39.5 25th 20.8 +1.8 16.1 8th 1.0 7.8 average 13%
Swanbourne 33.0 +3.5 43.1 26th 20.4 +2.4 13.1 8th 1.8 16.1 average 11%

Daily maximum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley24.228.729.530.425.322.322.526.029.530.632.433.431.828.530.626.229.333.933.932.333.029.232.134.736.738.034.837.129.228.2
Champion Lakes26.330.431.432.826.924.124.027.531.432.934.434.933.732.131.626.631.436.435.435.333.829.234.937.339.240.437.740.631.330.6
Garden Island HSF24.824.132.033.627.424.322.023.825.530.234.936.431.829.323.126.431.230.935.932.325.129.037.140.237.737.032.231.831.6
Gosnells City27.331.533.234.629.025.825.529.233.534.536.236.935.233.533.528.033.038.436.737.030.535.539.341.542.239.542.532.9
Jandakot Aero26.831.333.034.428.225.124.527.032.134.335.636.935.433.032.827.331.237.635.036.535.428.734.538.340.941.539.441.433.031.7
Medina Research Centre27.529.532.433.929.025.024.026.129.234.036.037.036.035.232.825.829.037.234.936.035.426.634.038.041.241.839.741.332.431.5
Pearce RAAF28.832.733.135.731.326.425.729.132.834.435.536.234.531.834.228.532.636.635.337.332.435.839.640.441.335.040.833.332.2
Perth Airport27.431.632.634.428.525.424.927.532.733.635.536.134.732.433.028.032.236.935.536.335.529.135.238.040.041.537.541.032.231.3
Perth Metro27.730.333.035.027.825.124.627.230.534.335.936.834.933.633.026.631.337.535.037.135.328.834.738.741.141.937.142.133.131.9
Rottnest Island24.924.229.932.726.124.223.222.124.728.332.729.834.333.228.924.124.830.230.335.930.426.227.431.339.536.636.135.529.430.2
Swanbourne27.727.233.635.627.025.024.426.130.034.136.937.335.333.730.825.830.037.731.338.232.527.933.539.441.843.137.038.934.032.7

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
Bickley16.614.814.413.017.516.312.910.612.813.615.617.919.621.119.014.412.814.919.017.718.320.517.817.020.620.923.724.018.813.013.5
Champion Lakes19.818.518.116.520.919.816.412.116.617.619.821.823.724.922.517.116.319.222.420.120.923.018.820.724.225.526.128.322.517.017.7
Garden Island HSF20.518.018.017.021.020.318.115.016.717.620.420.623.922.319.916.619.321.320.222.422.721.021.025.425.323.325.921.916.918.2
Gosnells City22.018.518.020.620.018.511.016.517.519.521.923.825.023.016.916.819.421.820.922.018.721.125.126.026.029.022.516.8
Jandakot Aero19.017.717.517.618.019.814.69.816.117.219.719.323.724.519.417.015.217.019.421.120.522.418.520.425.124.323.827.321.416.317.3
Medina Research Centre19.417.517.616.119.520.616.710.616.017.319.620.323.725.021.418.015.518.020.219.022.022.819.320.825.225.024.526.321.816.517.7
Pearce RAAF18.218.118.018.918.219.814.210.916.017.220.522.123.423.922.816.715.219.417.321.323.122.917.020.726.725.127.922.316.818.8
Perth Airport19.718.018.216.218.620.714.711.916.417.119.319.823.424.421.817.616.518.720.119.418.923.019.120.724.625.023.726.222.116.617.5
Perth Metro20.018.118.216.319.820.717.413.516.517.219.519.423.824.321.618.616.619.019.222.020.023.419.721.125.625.423.726.622.416.617.6
Rottnest Island20.418.418.217.620.619.718.316.117.218.120.622.123.724.122.719.717.220.222.521.922.921.920.721.023.725.824.826.422.116.918.6
Swanbourne19.417.817.618.119.919.917.513.116.717.719.919.924.124.022.118.215.919.220.822.523.122.219.820.825.226.625.028.021.616.418.1

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 - - - 10.2 - 3.2 0.2 - - - - - - - - - - - - 36.8 2.2 - - - - - 0.2 - - - -
Champion Lakes - - - 1.2 0.2 1.0 0.4 - - - - - - - - - - - - 13.6 3.4 - - - - - 1.8 - - - -
Garden Island HSF - - - 3.6 0.2 - - - - - - - -
- - - - - 18.4 2.4 - - - - - - - - - -
Gosnells City - - - 3.0 - 0.8 - - - - - - - - - - - - - 4.8 0.2 - - - - - 6.0 - - -
Jandakot Aero - - - - - 0.4 0.4 - - - - - - - - - - - - 10.4 1.6 - - - - - - - - - -
Jarrahdale - - - 0.8 - 2.4 - - - - - - - - - - - - - 60.6 - - - - - - - - - - -
Medina Research Centre - - - 4.6 - - - - - - - - - - - - - - - 29.6 1.0 - - - - - - - - - -
Mundaring


1.0
1.2 0.6











68.8 13.0




2.2



Pearce RAAF - - - - - - - - - - -
-

- - - - -

- 0.2 -
2.2 - - - -
Perth Airport - - - 2.2 - - - - - - - - - - - - - - - 14.2 6.0 - - - - - 4.8 - - - -
Perth Metro - - - 4.8 - - 0.6 - - - - - - - - - - - - 0.6 9.8 - - - - - 3.0 - - - -
Roleystone


















30.6










Rottnest Island - - - 1.0 - - - - - - - - - - - - - - - - - - - - - - - - - - -
Serpentine - - - - - - - - - - - - - - - - - - - 60.6 - - - - - - - - - - -
Swanbourne - - - - - - 0.2 - - - - - - - - - - - - 0.2 - - - - - - 1.4 - - - -

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

This statement was prepared before all data for the period were available. This may affect some of the statistics presented.

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 Tuesday 31 January 2012. 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, 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.

Records in this summary are based on sites with at least 10 years of data.

*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.

Further information

Media
(03) 9669 4057
Enquiries