Bureau of Meteorology logo
 
                           

Perth

                                                                                                   

Climate Overview

                             

Maps and graphs provide a summary of the rainfall, evaporation and temperature data for the reporting period.

 

Climate overview 2009-10

Rainfall

The total area-averaged rainfall over the Perth region during 2009-10 was 618 mm, which is below the mean annual rainfall of 804 mm. This can be attributed to stronger and more frequent than usual high pressure systems occurring over the south of Western Australia for much of the year, resulting in fewer than average cold fronts crossing the region. Figure C1 shows that rainfall across the entire region was below average to very much below average. 

Figure C1. Map of annual rainfall deciles for the Perth region during 2009-10

Figure C1. Map of annual rainfall deciles for the Perth region during 2009-10

During 2009-10, rainfall across the Perth region was highest along the Darling Escarpment ridge in the southern part of the region and lowest along the southeastern boundary (Figure C2). This distribution of rainfall during the reporting period is similar to the long-term average rainfall pattern (Figure C3). 

Figure C2. Map of total annual rainfall for the Perth region during 2009-10

Figure C2. Map of total annual rainfall for the Perth region during 2009-10 

Figure C3. Map of average annual rainfall for the Perth region, based on data collected between 1961-1990

Figure C3. Map of average annual rainfall for the Perth region, based on data collected between 1961-1990

During the reporting period, the Perth region experienced one of the driest summers on record (December to February). Almost no rainfall was recorded during this three-month period (Figure C4). 

Figure C4. Graph of total monthly rainfall for the Perth region during 2009-10 compared with the long-term percentiles for the region

Figure C4. Graph of total monthly rainfall for the Perth region during 2009-10 compared with the long-term percentiles for the region

 

Evapotranspiration

The total area-averaged evapotranspiration (ET) over the Perth region during 2009-10 was 697 mm, which is above the long-term mean annual ET of 666 mm and the 2009-10 rainfall total of 618 mm. Figure C5 shows that ET was generally average to above average across most of the region during 2009-10. In the southwestern area around Mandurah, ET was very much above average. Only a small area along the south-eastern boundary of the region had ET below average for the reporting period. 

Figure C5. Map of annual evapotranspiration deciles for the Perth region during 2009-10

Figure C5. Map of annual evapotranspiration deciles for the Perth region during 2009-10

During 2009-10, ET was highest along the Darling Escarpment ridge in the southern part of the region and lowest along the south-eastern boundary (Figure C6), similar to the rainfall. There was also a small area of low ET at the Peel-Harvey inlet near Mandurah. This distribution of ET across the region during the reporting period is similar to the long-term average ET pattern (Figure C7). 

Figure C6. Map of total annual evapotranspiration for the Perth region during 2009-10

Figure C6. Map of total annual evapotranspiration for the Perth region during 2009-10 

Figure C7. Map of average annual evapotranspiration for the Perth region, based on data collected between 1911-2010

Figure C7. Map of average annual evapotranspiration for the Perth region, based on data collected between 1911-2010

 

Temperature

Figure C8 shows that during 2009-10, the entire region recorded maximum daily temperatures that were very much above average. This can be attributed to stronger and more frequent than usual high pressure systems occurring over the south of Western Australia for much of the year. The result was fewer than average cold fronts crossing the region. 

Figure C8. Map of annual maximum daily temperature deciles for the Perth region during 2009-10 

Figure C8. Map of annual maximum daily temperature deciles for the Perth region during 2009-10

Maximum daily temperatures in the Perth region during 2009-10 were highest in the northern part of the region and lowest in the south near Harvey (Figure C9). This north-south temperature gradient is typical for the region (Figure C10). 

Figure C9. Map of annual mean maximum daily temperature for the Perth region during 2009-10

Figure C9. Map of annual mean maximum daily temperature for the Perth region during 2009-10 

Figure C10. Map of average annual maximum daily temperature for the Perth region, based on data collected between 1961-1990

Figure C10. Map of average annual maximum daily temperature for the Perth region, based on data collected between 1961-1990

During the reporting period, the Perth region experienced one of the hottest summers on record (December to February). The average monthly maximum daily temperatures for these three months were all above the 90th percentile for the region (Figure C11). 

Figure C11. Graph of average monthly maximum daily temperatures for the Perth region during 2009-10 compared with the long-term percentiles for the region

Figure C11. Graph of average monthly maximum daily temperatures for the Perth region during 2009-10 compared with the long-term percentiles for the region