Perth in October 2012: A hot and dry month

This statement was prepared before all data for the period were available. This may affect some of the statistics presented.
  • Rainfall: very much below average
  • Maximum temperature: highest on record at a number of sites
  • Minimum temperature: above average

Rainfall

Rainfall across the Perth metropolitan area during October 2012 was very much below average, with monthly rainfall totals generally in the 10 mm to 20 mm range, grading to close to 40 mm in the Perth hills.

A cold front crossed the Perth region early on the 3rd, with showers developing ahead of the front late on the 2nd and persisting into early on the 4th, although daily rainfall totals were generally light. A weak low moved across southwest WA on the 7th, resulting in generally light showers across the Perth region, and a cold front moved across southwest WA on the 13th, resulting in showers across the Perth region which persisted in the westerly flow following the front through to the morning of the 15th. Jarrahdale recorded the highest daily rainfall in the Perth metropolitan area for October 2012 during this event with 14.2 mm on the 14th. Another cold front crossed southwest WA on the 22nd resulting in generally light falls across Perth. Showers and thunderstorms moved over Perth from the north during the late morning and early afternoon on the 29th, associated with northerly winds, a hot morning, and a surface trough. Recorded rainfall totals were light however. Light showers were also observed over Perth from the afternoon of the 30th and into the 31st as cloudband moved over the region.

Perth Metro recorded 15.6 mm of rainfall on 6 rain days in October 2012, well below the long term October average of 52.3 mm on 8.8 rain days, and the 10th driest October at Perth Metro in 136 years of record. The wettest day during the month was the 4.4 mm in the 24 hours to 9am on the 14th. Historically, October rainfall in Perth has ranged from 1.0 mm in 1969 to 199.9 mm in 1890, while last October (2011), Perth Metro recorded 64.2 mm on 9 rain days.

The total rainfall for the 2012 year to date (January to October) at Perth Metro is 529.8 mm on 88 rain days, which is the equal 6th driest such period, equal with the 529.8 mm on 100 rain days in 1979. The average rainfall for the January to October period is 814.6 mm on 98.7 rain days, while the driest is 445.4 mm on 87 rain days in 2006.

Maximum temperature

Mean maximum temperatures in October 2012 were very much above average across the Perth region, with a number of sites observing their hottest October on record. Most sites recorded mean maxima between 2 °C and 3 °C above their October average.

October 2012 began with a very warm day across Perth, with temperatures in the low to mid-thirties in warm northerly winds ahead of a trough, and coastal and island sites recorded their hottest day of the month on the 1st. The trough moved inland on the 2nd, with temperatures dropping to the mid-twenties across Perth, before a cold front on the 3rd reduced temperatures further, and all sites observed their coolest day for the month on the 4th in the cold airmass behind the front, with temperatures in the mid-to-high teens. Warm conditions returned to the Perth area on the 10th and 11th with temperatures increasing to the high twenties and low thirties ahead of a cold front, and a similar pattern occured on the 20th and 21st. Maximum temperatures gradually rose from the 23rd to 26th before a hot weekend was observed on the 27th and 28th as temperatures reached the low to mid-thirties due to a deepening trough near the west coast. Conditions were particularly hot during the morning of the 28th, with most locations away from the coast on the coastal plain exceeding 36 °C, before temperatures moderated in the late morning and early afternoon as showers and thunderstorms moved over Perth from the north and the trough moved eastward. All sites away from the coast recorded their highest maximum for October 2012 in the morning on the 28th, with the highest in the metropolitan region being 36.5 °C at Gosnells City.

Perth Metro's mean daily maximum temperature in October was 25.0 °C, which was the 2nd warmest October in 116 years of record, only behind a mean maximum 25.8 °C registered in 1969. The average for October at Perth Metro is 23.1 °C. In terms of mean maximum temperature, six out of the eight warmest Octobers on record at Perth Metro have occurred since 2000 (Perth Metro's warmest Octobers were 1969, 2012, 2010, 2011, 1914, 2006, 2000 and 2008 in descending order). Last October (2011), Perth Metro experienced its 4th warmest October on record with 24.5 °C.

Daily maxima at Perth Metro ranged from a hot 36.2 °C on the 28th, the equal 8th hottest October day on record at Perth Metro, to a mild 19.2 °C on the 4th, the only sub-20 °C day during October 2012. Perth Metro has now recorded only one sub-20 °C day in both October 2012 and 2011, when previous to 2011 the lowest was two sub-20 °C days in 2010 and in 1969. The maximum temperature of 34.3 °C on the 1st was the earliest instance of a temperature of 34 °C or higher in spring since records commenced in 1897, with the previous records being 34.1 °C and 34.0 °C recorded on 12 October in 1968 and 1991 respectively. Perth Metro’s hottest day on record in October is 37.3 °C on 29 October 1967.

Perth Metro's mean daily maximum temperature for the 2012 year to date (January to October) is 25.1 °C, and is the 2nd warmest on record behind a January to October mean maximum of 25.2 °C observed in 2011. The average for the January to October period is 24.0 °C. Perth Metro has also seen a particularly warm two month period, with the September and October mean daily maximum temperature of 23.3 °C the warmest on record, breaking 23.2 °C set in 2010. The average for the September to October period is 21.6 °C.

Minimum temperature

Mean minimum temperatures in October 2012 were above average at most sites in the Perth, with mean minima generally between 11 °C and 14 °C, and mostly 1.0 °C to 1.5 °C above average.

After a mild start to the month in terms of overnight temperatures in the Perth area, where temperatures were mostly in the low to mid-teens, generally cool conditions were observed from the 4th to 8th, particularly on the morning of the 5th when most sites observed their lowest minimum temperature for the month. Jandakot observed the lowest temperature for October 2012 in the Perth area with 4.4 °C on the 5th. Warm overnight temperatures were observed from the 11th to 14th, with a trough located near the west coast and most sites observing their warmest night of the month during this period. Cool nights on the 16th, 18th and 23rd were interspersed with mild nights on the 17th and 22nd; while, warm overnight conditions returned to Perth on the 27th to 29th as a trough deepened near the west coast.

Perth Metro's mean daily minimum temperature in October 2012 was 12.5 °C, above the average of 11.3 °C. Daily minima ranged from a cool 8.5 °C on the 5th to a warm 18.4 °C on the 13th.

Sunshine

The mean daily sunshine hours for October was 9.8 hours which is close to the average of 9.6 hours.

Further information

Media
(03) 9669 4057
Enquiries

Extremes in October 2012
Hottest day 36.5 °C at Gosnells City on the 28th
Warmest days on average 25.9 °C at Gosnells City
25.9 °C at Pearce RAAF
Coolest days on average 22.2 °C at Bickley
Coldest day 16.0 °C at Bickley on the 4th
Coldest night 4.4 °C at Jandakot Aero on the 5th
Coolest nights on average 10.6 °C at Jandakot Aero
Warmest nights on average 15.1 °C at Rottnest Island
Warmest night 19.7 °C at Rottnest Island on the 28th
18.4 °C at Perth Metro on the 13th
Wettest overall 38.6 mm at Jarrahdale
Wettest day 14.2 mm at Jarrahdale on the 14th
Highest wind gust 76 km/h at Rottnest Island on the 2nd

Lowest total October rainfall for at least 10 years
Total rainfall
for October 2012 (mm)
Most recent October
at least this dry
Years since
drier
Average for
October
Pearce RAAF 7.6 5.8 in 2000 12 36.5



Record highest October mean daily maximum temperature
Mean daily maximum
temperature
for October 2012 (°C)
Previous warmest
for October
Years of
record
Average for
October
Medina Research Centre 25.2 24.4 in 2010 25 22.5
Jandakot Aero 24.8 = 24.8 in 2010 22 22.6
Swanbourne 25.1 24.0 in 2011 19 22.0
Gosnells City 25.9 25.5 in 2010 17 23.8
Garden Island HSF 23.0 22.3 in 2011 10 20.7



Summary statistics for October 2012
Maximum temperatures
for October
(°C)
Minimum temperatures
for October
(°C)
Rainfall
for October
(millimetres)
Mean for
October
2012
Diff
from
average
Highest for
October
2012
Mean for
October
2012
Diff
from
average
Lowest for
October
2012
Total for
October
2012
Average
for
October
Rank of
October
2012
Fraction of
October
average
Bickley 22.2 +1.2 32.2 28th 10.8 +1.3 6.8 5th 37.6 66.6 low 56%
Champion Lakes 24.0   34.4 28th 13.2   9.8 8th 17.2
Garden Island HSF 23.0 +2.3 33.0 1st 14.1 +0.8 10.8 5th 17.4 30.5 low 57%
Gosnells City 25.9 +2.1 36.5 28th 12.2 +0.6 6.5 16th 16.8 46.1 low 36%
Jandakot Aero 24.8 +2.2 35.5 28th 10.6 +1.1 4.4 5th 17.4 46.5 low 37%
Medina Research Centre 25.2 +2.7 36.0 28th 11.5 +1.2 6.4 5th 12.8 40.2 v low 32%
Pearce RAAF 25.9 +2.6 36.1 28th 11.2 +1.1 4.8 5th 7.6 36.5 v low 21%
Perth Airport 25.1 +2.5 36.0 28th 11.7 +1.5 6.7 8th 13.4 44.3 v low 30%
Perth Metro* 25.0 +1.9 36.2 28th 12.5 +1.2 8.5 5th 15.6 52.3 low 30%
Rottnest Island 22.7 +2.7 31.1 1st 15.1 +1.9 11.6 5th 7.4 37.1 v low 20%
Swanbourne 25.1 +3.1 35.2 1st 13.6 +1.5 8.0 5th        

Daily maximum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley30.922.816.116.019.726.017.820.321.723.426.523.820.417.417.621.320.420.520.226.227.616.819.221.022.825.029.832.221.720.2
Champion Lakes32.722.818.817.621.726.921.321.424.526.228.824.621.718.719.822.921.521.721.728.327.820.220.523.724.927.432.234.422.421.7
Garden Island HSF33.022.219.517.118.725.520.618.522.726.529.323.221.920.519.119.119.521.921.324.027.420.618.424.924.531.230.822.3
Gosnells City34.724.921.319.023.029.522.625.727.430.530.522.520.320.924.423.323.823.530.022.024.726.028.533.836.527.023.0
Jandakot Aero33.923.319.819.122.227.721.621.525.226.730.325.623.019.620.922.922.422.522.727.729.520.921.324.325.828.232.635.523.622.7
Medina Research Centre34.025.319.819.122.628.121.721.025.027.030.625.921.422.522.024.028.529.721.620.224.326.326.033.536.023.521.7
Pearce RAAF33.226.020.818.922.529.121.622.924.827.029.327.624.920.922.026.123.524.425.030.331.721.422.925.526.828.934.136.125.924.2
Perth Airport33.924.819.819.622.728.220.822.324.926.929.826.523.720.721.024.422.323.323.028.929.420.622.024.225.628.133.036.023.922.6
Perth Metro34.323.920.119.223.027.721.821.825.327.230.226.023.222.021.423.322.523.423.329.029.321.221.124.525.928.433.636.223.422.4
Rottnest Island31.122.419.817.718.923.821.119.921.325.628.522.922.120.520.420.620.821.922.623.023.721.319.821.321.923.630.930.622.620.2
Swanbourne35.222.520.219.921.127.422.221.725.527.330.823.622.821.222.521.922.723.428.628.021.720.925.726.828.933.635.023.822.1

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 minimum temperature
Central Coast (09)12345678910111213141516171819202122232425262728293031
Bickley11.715.911.08.56.87.410.88.210.67.913.513.915.011.710.29.411.410.311.310.013.112.77.68.28.37.911.515.614.79.410.1
Champion Lakes15.015.313.611.410.111.712.09.813.012.416.016.218.014.813.110.411.810.311.412.316.514.810.311.412.012.016.116.714.311.914.0
Garden Island HSF11.416.414.311.910.812.515.812.113.312.316.817.917.715.614.713.016.312.717.114.014.315.212.712.012.312.315.813.015.214.2
Gosnells City8.512.613.411.19.211.011.58.511.917.216.015.512.56.512.29.511.312.07.012.012.212.317.015.516.012.514.2
Jandakot Aero8.912.713.39.44.47.17.66.011.811.515.613.418.114.79.85.612.16.47.69.310.415.06.411.011.411.513.09.812.78.613.1
Medina Research Centre10.013.313.710.06.411.113.89.411.911.811.915.211.77.212.27.513.010.115.28.811.011.711.913.512.710.014.2
Pearce RAAF11.613.613.49.24.810.48.47.510.711.916.913.517.211.612.45.110.46.59.38.211.515.37.111.012.312.215.013.213.210.612.6
Perth Airport12.013.714.79.77.510.010.36.712.911.614.613.217.915.311.97.012.57.08.89.413.715.47.612.012.111.912.513.313.49.414.1
Perth Metro10.515.015.210.78.511.210.68.913.311.916.413.418.415.812.78.813.59.210.210.812.115.610.112.112.511.913.712.114.513.014.2
Rottnest Island16.317.415.213.111.613.015.114.014.412.816.317.817.315.414.014.016.115.216.114.816.814.613.312.713.013.617.419.717.314.914.5
Swanbourne15.016.213.111.38.011.415.110.813.111.817.017.418.010.514.411.916.111.514.714.911.011.712.312.616.115.616.612.313.3

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 - - 6.8 2.0 - - - 11.6 - - - - - 8.6 2.0 0.4 - - - 0.2 - 4.6 1.2 - - - - - 0.2 - -
Champion Lakes - - 5.4 0.2 - 0.2 - 0.4 - - - - - 4.6 0.2 0.4 0.2 - - - - 4.4 1.2 - - - - - - - -
Garden Island HSF - - 1.6 2.0 0.2 - - - - - - - - 1.8 1.0 0.6 - - - 0.2 - 9.4 0.6 -
- - - - -
Gosnells City - - 3.4 2.0 - - - - - - - »» 3.0 2.8 1.2 - - - - - - 4.4 - - - - - - - - -
Jandakot Aero - - 5.0 1.4 - - - 0.4 - - - - - 3.8 1.2 0.8 - - - - - 4.4 0.4 - - - - - - - -
Jarrahdale 0.2 - 8.0 0.8 0.2 - - 0.2 - - - - - 14.2 4.0 0.8 - 0.2 - 0.2 0.2 6.0 3.6 - - - - - - - -
Medina Research Centre - - 3.2 0.8 - - - - - - - - »» »» 2.4 - - - - - - 6.4 - - - - - - - - -
Pearce RAAF - - 1.4 0.2 - - 1.2 1.0 - - - - - 0.8 1.6 - - - - - - 0.8 0.4 0.2 - - - - - - -
Perth Airport - - 1.0 1.2 - - - 2.0 - - - - - 4.0 1.4 - - - - - - 2.4 0.8 - - - - - 0.6 - -
Perth Metro - - 3.8 0.4 - - - - - - - - - 4.4 2.2 - - - - - - 3.8 1.0 - - - - - - - -
Roleystone

6.4 0.6























0.4

Rottnest Island - - 1.2 0.2 - - - 1.2 - - - - - 1.2 - - - - - - - 3.2 0.4 - - - - - - - -
Serpentine - - 3.4 1.4 0.2 - - - - - - - - 3.4 0.8 1.0 - - - - - 6.0 2.0 - - - - - - - -
Swanbourne - - 2.6 1.6 - - - - - - - - - 4.8
0.2 - - - - - 3.8 0.4 - - - - - 0.2 - -

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 11 am on Wednesday 31 October 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.
The median is sometimes more representative than the mean of long-term average rain.

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.

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