Perth in September 2013: Wet with mild nights

  • Rainfall: wettest September on record for a number of sites
  • Maximum temperature: near average
  • Minimum temperature: warmest September on record for most sites

Rainfall

Rainfall across the Perth metropolitan area during September 2013 was above to very much above average, with coastal sites at Swanbourne and Garden Island, as well as Bickley in the Perth hills recording their wettest September on record. This was the result of persistent westerly winds during September in the region with the frequent passage of cold fronts, lows and troughs. Monthly rainfall totals ranged from about 110 mm on Rottnest Island, up to 170 mm on the coastal plain, and 290 mm in the hills.

A westerly airstream produced isolated light showers in the Perth metropolitan area on the 1st and 2nd before a cold front and associated cloudband moved through western parts of WA bringing moderate rainfall to much of Perth on the 3rd and 4th as well as strong winds. A deep trough near the west coast produced showers and thunderstorms in the Perth area on the 7th with moderate to heavy falls in the northern suburbs and in the hills. Two cold fronts moved through the Southwest Land Division (SWLD) on the 10th and 11th with moderate falls on both days on the coastal plain and in the hills, and a 93 km/h wind gust reported at Rottnest Island in the early morning on the 11th. A strong cold front and associated low moved slowly across the SWLD from the evening of the 13th to the 14th, bringing isolated thunderstorms, strong winds, and showers with moderate to heavy falls across Perth. Rottnest Island recorded a daily rainfall of 42.0 mm on the 14th, which was the highest daily rainfall reported in the Perth metropolitan area in September 2013, and the wettest September day on the island for exactly 29 years, since 45.6 mm was recorded on 14 September 1984. Garden Island recorded a daily rainfall of 41.2 mm on the 14th, which was the wettest September day at the site in 12 years of record.

Another strong cold front moved through the SWLD on the 16th and 17th producing moderate falls at most Perth sites, along with strong winds. A westerly airstream in the wake of the front continued to bring light showers between the 18th and the 20th before two strong cold fronts moved across the SWLD on the 22nd and 23rd bringing squally winds and heavy showers to the Perth area. A number of weak cold fronts and a westerly airstream continued to produce light rainfall in the Perth area between the 24th and 27th. A cold front moved through the SWLD on the 29th bringing light to moderate rainfall across the Perth area.

Perth Metro recorded 144.2 mm of rainfall on 20 rain days during September 2013, which was the 8th wettest September on record since records commenced in 1876 and the wettest September for 40 years, since a total of 146.0 mm was recorded in 1973.

Maximum temperature

Mean maximum temperatures in September 2013 were near average across the Perth metropolitan area. Mean maxima ranged from the mid-teens in the hills to the low twenties on the coastal plain.

Mild days were experienced during the first two days of September 2013, and again on the 6th, 9th, 20th and 21st, with daily maximum temperatures generally in the low 20 ºC. The 2nd was the warmest day of the month for most Perth sites with a maximum of 24.1 ºC at Gosnells City the highest temperature recorded in the metropolitan area during the month. Cool days were reported on the 14th, 15th, 17th and 30th, with most sites recording their coolest day of the month on the 14th, however Bickley recorded a maximum of 13.2 ºC on the 17th, the lowest maximum temperature in Perth in September 2013.

Perth Metro's mean maximum temperature in September 2013 was 20.2 °C, which equalled the long-term average.  Daily maxima ranged from a cool 17.0 ºC on the 14th to a mild 23.6 ºC on the 2nd.

Minimum temperature

Mean minimum temperatures in September 2013 were very much above average across the Perth metropolitan area, with a number of sites recording their warmest September on record, including Rottnest Island in 133 years of recording. Mean minima were generally in the 10 ºC to 12 °C range on the coastal plain and in the hills, and in the 13 ºC to 14 ºC range on the offshore islands.

Nights in September 2013 were mostly cool to mild, with the first three days being very mild and most sites recorded their warmest night of the month on the 2nd. Swanbourne recorded a minimum of 17.2 ºC on the 1st, which exceeded the previous record at Swanbourne in 21 years of recording of 17.0 ºC set on 20 September 199, whilst Rottnest Island recorded a minimum of 17.6 ºC on the 2nd, the highest minimum temperature in Perth during September 2013. Cold nights were experienced on the coastal plain on the 6th and 9th, with most sites recording their lowest temperature of the month on the 6th, including Jandakot Aerodrome with the lowest in Perth in September 2013 with a minimum of 3.3 ºC.

Perth Metro's mean daily minimum temperature in September 2013 was 11.6 °C, which was well above the average of 9.5 °C, and the warmest September for 24 years since a mean of 11.6 °C was recorded in 1989. During September 2013, Perth Metro recorded no nights with minimum temperature 5 °C or less. This was the first time in 13 years that the current Perth Metro site at Mount Lawley had not recorded a night of 5 °C or less in September. Daily minima ranged from a cold 5.3 °C on the 6th to a mild 16.2 °C on the 2nd.

Sunshine & Phenomena

Perth recorded an average daily sunshine of 6.5 hours in September 2013, which is below the long-term average of 7.7 hours, and the least sunniest September for 12 years, since a mean of 6.5 hours per day was recorded in September 2001.

A cold front on the 16th produced a 93 km/h wind gust in the afternoon at Ocean Reef and minor damage was reported in the East Perth and Rockingham areas, mostly related to water inundation.

Two strong cold fronts moved across the SWLD on the 22nd and 23rd producing squally winds and showers in the Perth area. Wind gusts over 90 km/h were reported in the Perth metropolitan area late on the 22nd and early on the 23rd with the highest being 107 km/h at Rottnest Island. Four thousand homes lost power as a result, whilst a tornado was reported in Maddington in the southeast suburbs and 15 houses were damaged.

Further information

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Extremes in September 2013
Hottest day 24.1 °C at Gosnells City on the 2nd
Warmest days on average 20.5 °C at Gosnells City
Coolest days on average 16.7 °C at Bickley
Coldest day 13.2 °C at Bickley on the 17th
Coldest night 3.3 °C at Jandakot Aero on the 6th
Coolest nights on average 9.6 °C at Bickley
Warmest nights on average 13.9 °C at Rottnest Island
12.5 °C at Swanbourne
Warmest night 17.6 °C at Rottnest Island on the 2nd
17.4 °C at Gosnells City on the 2nd
Wettest overall 295.8 mm at Bickley
Wettest day 42.0 mm at Rottnest Island on the 14th
41.8 mm at Jarrahdale on the 30th
Highest wind gust 107 km/h at Rottnest Island on the 22nd

Record highest September daily rainfall
Highest daily rainfall
in September 2013 (mm)
Previous wettest
for September
Years of
record
Garden Island HSF 41.2 on the 14th 21.2 on the 4th in 2012 12



Record highest total September rainfall
Total rainfall
for September 2013 (mm)
Previous wettest
for September
Years of
record
Average for
September
Perth Airport 169.4 163.0 in 1971 70 73.6
Pearce RAAF 163.9 136.5 in 1971 59 70.0
Roleystone 252.8 225.6 in 1971 46 115.1
Bickley 295.8 226.9 in 1973 45 127.4
Swanbourne 160.8 136.8 in 1996 20 84.8
Garden Island HSF 151.6 95.0 in 2005 12 68.0



Record highest September daily minimum temperature
Highest daily minimum
temperature
in September 2013 (°C)
Previous warmest
for September
Years of
record
Average for
September
Swanbourne 17.2 on the 1st 17.0 on the 20th in 1994 21 10.9



Record highest September mean daily minimum temperature
Mean daily minimum
temperature
for September 2013 (°C)
Previous warmest
for September
Years of
record
Average for
September
Jandakot Aero 10.8 10.0 in 1989 23 8.1
Rottnest Island 13.9 13.8 in 1983 133 12.8
Gosnells City 11.5 11.1 in 2006 20 10.0
Swanbourne 12.5 11.9 in 2000 20 10.9
Bickley 9.6 9.2 in 2000 19 8.2
Garden Island HSF 13.7 12.6 in 2006 11 11.8


Summary statistics for September 2013
Maximum temperatures
for September
(°C)
Minimum temperatures
for September
(°C)
Rainfall
for September
(millimetres)
Mean for
September
2013
Diff
from
average
Highest for
September
2013
Mean for
September
2013
Diff
from
average
Lowest for
September
2013
Total for
September
2013
Average
for
September
Rank of
September
2013
Fraction of
September
average
Bickley 16.7 -0.7 19.9 2nd 9.6 +1.4 6.7 17th 295.8 127.4 highest 232%
Champion Lakes 19.2   23.3 2nd 11.7   7.5 16th 166.4
Garden Island HSF 19.0 +0.2 21.3 2nd 13.7 +1.9 9.7 6th 151.6 68.0 highest 223%
Gosnells City 20.5 -0.2 24.1 2nd 11.5 +1.5 7.1 6th        
Jandakot Aero 19.7 -0.3 22.5 2nd 10.8 +2.7 3.3 6th 173.2 88.4 v high 196%
Pearce RAAF 20.2 +0.2 23.3 2nd 10.3 +1.6 5.6 9th 163.9 70.0 highest 234%
Perth Airport 20.1 0.0 22.7 9th 10.6 +1.8 4.3 6th 169.4 73.6 highest 230%
Perth Metro 20.2 0.0 23.6 2nd 11.6 +2.2 5.3 6th 144.2 80.9 v.high 178%
Rottnest Island 19.2 +0.5 21.6 2nd 13.9 +1.1 10.5 17th 107.0 58.5 v.high 133%
Swanbourne 20.1 +0.3 23.0 6th 12.5 +1.6 8.4 6th 160.8 84.8 highest 186%

Daily maximum temperature
Central Coast (09)123456789101112131415161718192021222324252627282930
Bickley19.319.917.516.017.519.714.817.219.517.014.316.017.513.915.318.313.216.016.917.118.614.316.516.016.816.916.617.616.314.6
Champion Lakes21.123.320.417.119.921.918.419.421.219.517.718.120.315.917.120.516.418.718.919.720.618.419.919.218.220.618.718.919.016.2
Garden Island HSF21.221.320.817.819.219.317.317.820.320.417.818.319.816.016.119.917.518.819.420.120.518.419.819.319.219.518.719.819.115.2
Gosnells City22.324.121.518.520.823.319.520.522.521.318.419.220.516.817.821.916.720.020.521.122.418.821.820.320.321.021.0
Jandakot Aero21.622.521.117.819.721.919.119.921.719.618.518.920.416.517.620.017.119.919.621.121.318.421.019.919.320.019.520.319.317.2
Medina Research Centre23.223.421.418.320.322.119.819.3
Pearce RAAF22.123.320.918.220.521.718.520.122.521.818.319.220.816.217.821.717.319.420.821.423.218.520.820.519.820.620.221.020.917.7
Perth Airport22.722.721.418.220.322.418.120.722.721.517.719.520.116.617.821.817.419.720.321.321.918.320.620.219.220.419.720.520.617.3
Perth Metro22.423.621.018.520.422.419.020.122.420.518.519.120.317.017.721.217.719.820.621.721.618.921.120.519.620.720.320.220.817.3
Rottnest Island21.421.620.617.719.719.118.218.420.720.018.119.019.615.417.619.716.819.419.820.120.618.420.319.919.119.919.719.620.016.7
Swanbourne21.122.620.518.520.523.018.920.321.819.719.219.321.116.317.719.817.919.920.821.321.818.620.420.119.820.320.421.421.617.1

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)123456789101112131415161718192021222324252627282930
Bickley12.514.413.17.68.57.28.88.77.610.810.410.610.09.47.86.96.78.511.210.38.89.89.912.910.98.97.98.911.06.9
Champion Lakes15.016.613.59.810.67.712.29.59.111.613.013.112.011.811.27.59.611.314.112.69.213.013.315.412.912.08.411.413.69.7
Garden Island HSF16.616.716.112.914.19.713.112.710.514.813.713.312.812.413.19.811.012.314.815.314.513.913.016.615.315.314.815.516.310.6
Gosnells City13.017.412.99.110.77.112.38.47.511.212.812.912.511.29.511.614.812.08.89.812.015.813.511.19.112.9
Jandakot Aero14.015.613.110.49.13.310.67.04.610.413.213.310.611.910.75.910.19.914.311.67.512.613.615.613.69.48.49.614.18.9
Medina Research Centre16.016.114.111.09.45.011.57.85.4
Pearce RAAF14.915.811.38.76.55.711.87.35.69.012.712.812.311.310.86.49.59.911.511.99.013.212.915.711.47.37.66.610.89.3
Perth Airport13.516.011.88.98.54.311.16.66.39.812.613.211.911.411.05.98.710.814.811.68.913.513.315.413.79.17.68.211.19.4
Perth Metro14.316.214.211.79.05.312.29.36.711.113.413.011.711.911.47.510.211.714.812.19.513.513.415.314.710.510.09.515.49.6
Rottnest Island16.817.617.211.713.112.913.714.012.915.613.513.614.012.312.213.010.512.014.214.814.612.412.615.915.014.313.614.716.411.2
Swanbourne17.216.514.211.510.98.411.510.99.012.813.313.312.511.611.69.19.912.213.714.010.913.112.215.514.714.413.912.216.09.1

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) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Bickley 2.0 0.6 - 24.8 0.2 - 21.0 1.8 0.2 - 28.6 31.8 0.8 33.0 7.4 0.2 33.6 5.4 8.0 3.2 8.0 32.4 29.2 5.6 4.0 0.2 6.0 - - 7.8
Champion Lakes 0.4 0.2 - 14.8 - - 2.4 6.6 - - 17.8 16.4 - 26.0 2.6 - 19.4 1.8 1.8 4.4 3.0 14.8 17.0 2.8 0.6 0.2 3.8 - - 9.6
Garden Island HSF - 1.4 0.4 14.4 - - - 0.2 - - 13.4 10.6 0.8 41.2 9.2 - 11.2 1.0 1.6 0.4 1.0 9.8 5.0 1.0 1.4 - 3.0 - 2.0 22.6
Gosnells City »» »» »» 16.0 0.1 - - - - - 24.4 27.8 0.6 24.2 6.2 - 14.2 2.0 2.6 1.6 2.0 15.2 11.0 2.0 0.4 0.6
- -
Jandakot Aero - 2.4 - 12.6 - - 0.4 0.6 - - 18.0 15.4 0.6 30.6 5.8 0.2 15.6 0.8 2.8 13.8 2.2 17.8 9.2 3.0 0.8 - 3.8 - 0.2 16.6
Jarrahdale 0.6 - 0.2 26.4 - 0.2 0.4 0.2 - 0.2 20.8 30.0 0.6 19.8 7.8 0.2 20.6 2.4 6.0 13.0 3.4 20.8 24.2 6.4 1.2 0.8 15.6 - 3.4 41.8
Pearce RAAF 1.4 - - 10.6 - - 10.8 2.0 - - 16.2
0.4 37.8 16.2 - 13.4 0.2 0.8 - 1.0
11.4 3.0 0.8 - 2.2 - - 5.4
Perth Airport 0.4 - - 8.2 - - 39.4 2.0 - - 17.2 12.2 0.4 26.2 4.0 - 11.8 0.8 2.2 1.0 1.6 13.6 12.2 2.2 1.2 - 4.0 - - 8.8
Perth Metro 0.2 - - 11.2 - - 4.2 1.4 - - 19.4 16.8 - 20.0 11.2 0.2 11.8 0.6 3.4 2.6 2.0 14.0 10.2 2.6 1.6 - 3.0 - - 7.8
Roleystone 1.8 0.2 0.4 27.2 0.2 - 2.6 8.8 - 0.2 22.0 25.4 0.2 29.8 9.0 0.2 25.2 - 7.6 - 8.0 24.2 23.8 6.0 1.6 0.8 6.8 - 1.0 19.8
Rottnest Island - - - 2.6 - - - 0.8 - - 9.0 3.2 0.8 42.0 9.0 - 6.4 0.6 1.0 3.0 1.4 7.6 3.2 - 0.2 - 3.0 - - 13.2
Serpentine 0.4 - - 30.2 0.2 - - - - - 15.0 23.6 0.2 26.4 4.4 0.2 16.2 2.2 3.0 5.2 3.2 8.4 9.8 2.0 0.4 - 5.0 - 0.4 22.4
Swanbourne - 0.4 0.4 16.2 - - 0.2 0.8 0.2 - 18.0 8.8 0.4 39.4 10.8 - 6.8 1.8
1.0 1.8 17.6 14.2 1.4 0.8 - 2.4 - - 14.6

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 Tuesday 1 October 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, 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.

The ACORN-SAT dataset is being used for temperature area averages from December 2012 onwards. The major change from earlier datasets is that the ACORN-SAT dataset commences in 1910, rather than 1950, and hence rankings are calculated using a larger set of years.

Further information

Media
(03) 9669 4057
Enquiries