Perth in April 2012: Wet start and finish

This statement was prepared before all data for the period were available. This may affect some of the statistics presented.
  • Rainfall: Near average to above average
  • Maximum temperature: Near average to above average
  • Minimum temperature: Near average to above average

Rainfall

Rainfall totals in April 2012 were generally near average in the Perth Metropolitan area, however some sites recorded above average rainfall, particularly in the western suburbs, where heavy falls in the last two days of April significantly boosted totals. Contributions also came from a number of other cold front and a low passages during the month. Roleystone observed the highest total in the Perth area for the month with 87.4 mm, which is also its wettest April since the 139.6 mm in 2008.

A westerly airflow produced mainly light showers to the coastal plain in the Perth area in the first few days of April, though sites in the Perth hills received moderate falls. A cold front moving through the Perth area brought further light to moderate rainfall on the morning of the 5th, but was followed by a lengthy dry period of almost two weeks before a cold front passed through the Perth metropolitan area on the 18th bringing rainfall totals of generally less than 10 mm. The 22nd saw the passage of a weak cold front with daily totals of less than 5 mm across the Perth area before a low pressure system off the west coast moved through the Perth area on the 28th and 29th and brought significant rainfall, with totals in the 20 to 60 mm range during the event. The daily rainfall total of 56.2 mm on the 28th at Swanbourne was the highest daily total of the month in the Perth area, and was Swanbourne's second wettest April day in 17 years of record.

Perth Metro recorded 69.2 mm of rainfall during April 2012, which is the wettest April for 4 years since 153.6 mm was recorded on 13 rain days in 2008. For the first four months of the year (January to April), Perth Metro has recorded 111.8 mm of rainfall on 16 rain days, which is above the average of 85.5 mm on 15.2 rain days and the wettest start to the year (January to April) since 215.4 mm was recorded on 18 rain days in 2008.

Maximum temperature

Mean maximum temperatures in April 2012 were generally in the mid-twenties across the Perth Metropolitan area, and in the near average to above average range.

The Perth area experienced a hot day on the 10th with daily maxima for most sites in low to mid-thirties as a strong high pressure system in the Bight directed hot northerly air over the Perth area. Pearce and Perth Airport recorded the highest temperature of the month with 35.9 °C on the 10th. The coolest day of the month over the Perth area was on the 21st as the result of a cool southerly flow, with daily maxima in the high teens and low twenties. The temperature at Bickley only reached 17.8 °C, the coldest day of the month in the Perth metropolitan area.

Perth Metro's mean maximum temperature in April was 26.4 °C, which is close to the April average of 25.7 °C. Perth Metro's maxima ranged from 21.9 °C on the 21st to a hot 35.4 °C on the 10th.

The mean maximum temperature at Perth Metro for the first four months of 2012 (January to April) was 30.6 °C, which is the 3rd hottest start to the year since records commenced in 1897, only behind 31.5 °C in 2011 and 31.3 °C in 1978. April also continues the run of above average mean monthly maxima at Perth Metro since August 2010, where 19 of the past 21 months have seen above average mean monthly maximum temperatures.

Minimum temperature

Mean minimum temperatures in April 2012 were generally in the 13 to 17 °C range, and close to average or above average for most sites in the Perth metropolitan area.

Most sites experienced a relatively warm start and end to April with warm nights (a warm night is daily minimum temperature 20 °C or above) recorded at most sites on the 4th and again on the 28th due to cloudy and overcast conditions following a warm day. The overnight temperature of 23.4 °C at Pearce on the 28th was the warmest night of the month for the Perth area. Average to below average minimum temperatures were recorded during middle parts of the month, with the coolest nights at most sites being recorded on the 6th and 21st. A minimum of 5.6 °C at Pearce RAAF on the 21st was the coldest night recorded in Perth during April 2012.

Perth Metro's mean daily minimum temperature in April was 14.3 °C, close to the average of 13.6 °C. Daily minima ranged from a cool 9.2 °C on the 21st to a warm 20.9 °C on the 4th.

Sunshine

Perth recorded an average daily sunshine of 8.0 hours in April 2012, which was the least sunniest April for 8 years since an average of 7.9 hours per day was recorded in 2004. The average sunshine for Perth in April is 8.3 hours per day.

Further information

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Extremes in April 2012
Hottest day 35.9 °C at Pearce RAAF on the 10th
35.9 °C at Perth Airport on the 10th
Warmest days on average 27.4 °C at Pearce RAAF
Coolest days on average 23.4 °C at Bickley
Coldest day 17.8 °C at Bickley on the 21st
Coldest night 5.6 °C at Pearce RAAF on the 21st
Coolest nights on average 12.7 °C at Jandakot Aero
Warmest nights on average 18.0 °C at Rottnest Island
15.8 °C at Swanbourne
Warmest night 23.4 °C at Pearce RAAF on the 28th
Wettest overall 87.4 mm at Roleystone
Wettest day 56.2 mm at Swanbourne on the 29th
Highest wind gust 67 km/h at Rottnest Island on the 5th




Summary statistics for April 2012
Maximum temperatures
for April
(°C)
Minimum temperatures
for April
(°C)
Rainfall
for April
(millimetres)
Mean for
April
2012
Diff
from
average
Highest for
April
2012
Mean for
April
2012
Diff
from
average
Lowest for
April
2012
Total for
April
2012
Average
for
April
Rank of
April
2012
Fraction of
April
average
Bickley 23.4 -0.1 32.1 10th 13.3 +0.8 6.6 6th 78.8 56.2 average 140%
Champion Lakes 25.5   34.3 10th 15.5   9.9 21st 68.2
Garden Island HSF 24.3 +0.6 29.5 10th 16.5 +0.7 11.8 6th 47.4 44.8 average 106%
Jandakot Aero 26.1 +0.4 34.6 10th 12.7 +0.4 6.9 21st 69.4 43.5 high 160%
Medina Research Centre 26.3 +0.8 35.3 10th 14.3 +1.1 9.8 6th 57.0 40.3 high 141%
Pearce RAAF 27.4 +1.1 35.9 10th 13.4 +0.1 5.6 21st 50.0 35.0 high 143%
Perth Airport 26.5 +1.0 35.9 10th 14.0 +1.1 7.0 21st 53.4 41.4 average 129%
Perth Metro 26.5 +0.8 35.4 10th 14.3 +0.7 9.2 21st 69.2 43.9 high 158%
Rottnest Island 24.7 +1.0 32.5 10th 18.0 +0.8 12.5 6th 35.8 36.1 average 99%
Swanbourne 26.2 +1.0 33.8 10th 15.8 +0.8 11.0 6th 85.2 39.5 v high 216%

Daily maximum temperature
Central Coast (09)123456789101112131415161718192021222324252627282930
Bickley20.821.322.322.719.520.026.827.426.632.130.527.824.323.425.123.823.020.919.419.217.819.919.422.325.928.325.822.819.5
Champion Lakes23.523.724.824.621.521.829.429.227.834.331.428.725.225.226.324.924.423.222.821.220.021.621.824.729.230.728.926.022.8
Garden Island HSF24.324.425.424.920.722.924.426.724.329.529.324.622.123.723.224.124.624.121.820.419.620.122.825.827.529.326.925.223.1
Gosnells City24.825.125.826.422.024.531.030.729.227.027.926.524.523.422.621.023.022.826.032.230.026.524.3
Jandakot Aero24.925.825.826.322.322.729.529.526.834.631.128.225.226.326.525.325.524.822.722.620.922.322.625.428.831.429.326.723.9
Medina Research Centre26.125.426.626.821.522.930.029.226.935.331.928.424.824.826.525.625.926.223.121.620.422.522.925.829.532.029.326.224.5
Pearce RAAF25.927.126.427.423.123.330.230.929.535.934.832.926.627.028.727.026.825.223.123.121.823.023.126.728.932.529.929.924.2
Perth Airport24.226.225.826.522.923.330.130.027.535.932.430.425.726.026.926.026.124.722.422.321.422.722.626.229.631.929.725.923.6
Perth Metro24.425.526.525.622.423.629.929.827.535.431.930.825.426.026.526.126.425.023.022.321.922.223.126.429.532.029.525.523.8
Rottnest Island24.425.126.525.022.221.324.925.625.632.529.424.823.523.424.024.924.724.523.021.320.720.521.324.929.129.325.425.023.7
Swanbourne25.026.026.526.022.123.929.227.325.433.830.727.924.425.625.025.525.925.422.823.021.322.423.927.230.532.829.625.924.4

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
Bickley12.716.116.717.614.06.69.712.514.715.217.316.114.512.711.714.313.112.710.610.89.310.48.28.813.113.417.818.516.113.8
Champion Lakes13.318.218.920.616.510.613.516.514.417.319.615.014.914.013.914.413.215.114.713.49.911.011.614.016.816.020.322.118.016.1
Garden Island HSF14.420.419.021.418.211.814.217.013.415.919.613.618.616.215.516.615.318.214.514.913.914.312.814.517.516.019.521.318.218.1
Gosnells City13.017.818.615.910.015.517.015.016.113.013.013.814.614.112.710.511.012.815.414.5
Jandakot Aero10.618.219.020.416.110.38.815.811.112.013.110.813.69.28.611.29.512.49.79.56.98.89.19.914.510.717.121.717.115.9
Medina Research Centre11.119.519.121.116.19.810.816.012.012.216.912.315.911.710.213.110.714.411.011.69.811.511.012.917.114.419.022.718.016.0
Pearce RAAF11.914.717.618.816.311.314.515.714.112.516.19.715.08.38.310.59.710.614.59.15.68.28.610.817.417.219.123.417.116.7
Perth Airport12.118.918.120.516.410.712.216.213.914.117.612.716.09.99.411.110.512.112.411.07.08.810.810.417.016.019.422.217.316.7
Perth Metro13.019.219.520.916.510.811.516.013.714.516.513.116.611.811.312.912.611.713.011.59.211.011.312.215.610.917.620.117.717.0
Rottnest Island17.520.019.221.217.312.514.417.619.119.221.719.519.717.517.418.818.019.316.116.815.714.913.915.317.119.921.622.618.117.9
Swanbourne15.018.819.421.116.111.013.916.213.416.317.715.716.013.913.615.214.219.313.513.111.612.512.013.017.115.920.722.417.816.1

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)123456789101112131415161718192021222324252627282930
Bickley - 1.2 15.6 - 14.2 - - - - - - - - - - - - - 5.0 - - 0.2 - - - - - - 27.0 15.6
Champion Lakes - 0.4 8.0 - 8.0 - - - - - - - - - - - - - 2.0 - - - - - - - - - 34.4 15.4
Garden Island HSF - 0.2 5.2 - 5.8 - - - - - 0.2 - - - - - - 4.2 3.2 - - 4.2 - - - - - - 13.2 11.2
Gosnells City - 1.0 5.8 0.1 8.8 0.1 - - - - - - - - - - - - 6.4 - - 0.2 - - - - - - 39.0 10.9
Jandakot Aero - 1.6 10.2 0.2 12.4 - - - - - - - - - - - - - 0.8 - - 0.8 - - - - - - 28.0 15.4
Jarrahdale 0.2 0.6 20.6 1.0 11.6 - 0.2 - - 0.2 0.2 - - 0.2 0.2 - - 2.4 11.6 - 0.2 1.2 0.2 - - - - - 14.0 22.4
Medina Research Centre - 0.5 6.6 0.1 6.1 - - - - - - - - - - - - 0.9 6.0 - - 1.4 - - - - - - 21.8 13.6
Mundaring
1.6 11.2
12.0


0.2 0.2







3.0

0.2





18.0 11.0
Pearce RAAF - 0.2 3.6 - 8.8 - - - - - - - - - - - - - 3.2 - - 0.4 - - - - - - 23.0 10.8
Perth Airport - - 4.4 - 11.2 - - - - - - - - - - - - - 4.4 - - 0.4 - - - - - - 25.2 7.8
Perth Metro - 0.6 4.6 - 12.6 - - - - - - - - - - - - - 4.2 - - 0.2 - - - - - - 40.8 6.2
Roleystone
2.2 14.0 0.2 12.2











0.2 8.0








»» 50.6
Rottnest Island - - 3.0 - 11.0 - - - - - - - - - - - - - 1.0 - 0.2 3.0 - - - - - - 13.0 4.6
Serpentine - 1.2 7.8 - 7.4 0.2 - - - - - - - - - - - 0.8 4.2 - - 2.0 - - - - - - 13.4 23.2
Swanbourne - - 3.8 - 14.2 - - - -

- - - - - - - 1.8 - - 1.6 - - - - - - 56.2 7.6

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

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 4 pm on Monday 30 April 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