Perth
Climate overview

Rainfall across the Perth region was below average for the 2012–13 year (Figure C1). The total area-averaged rainfall over the Perth region during the 2012–13 year was 586 mm, which is well below the long-term area-averaged rainfall of 780 mm (based on the 1900–2013 period).

These rainfall conditions represent a decrease in rainfall compared to the 2011–12 year when rainfall was slightly above average (see the 2012 Account). The below average rainfall contributed to below average flows in the major river systems in the region (see Water overview) as well as decreased inflows into the major water storages during the 2012–13 year (see the Surface water section of the 'Water resources and systems' note).

Figure C1  Map of annual rainfall deciles for the Perth region during the 2012–13 year

Annual rainfall ranged from more than 800 mm in the southern and central parts of the region to less than 300 mm in the far southeast (Figure C2). 

Figure C2  Map of total annual rainfall for the Perth region during the 2012–13 year

Generally below average rainfall was experienced across much of Australia during the 2012–13 year. There were no strong influences from large-scale climate drivers during the year. Conditions in the Pacific Ocean were neutral and a negative Indian Ocean Dipole event developed at the end of the 2012–13 year.

The area-averaged monthly rainfall varied greatly during the 2012–13 year (Figure C3). Monthly rainfall during July 2012 and June 2013 were the driest on record with area-averaged rainfall less than 20% of the long-term average. In contrast, rainfall observed during November–December 2012 and March 2013 was above the 90th percentile.

Figure C3  Graph of total monthly rainfall for the Perth region during the 2012–13 year compared with the long-term average and percentiles for the region

Evapotranspiration across the Perth region was generally average to above average for the 2012–13 year (Figure C4). The above average evapotranspiration reflects the very much above average temperature experienced across the entire region throughout the year (see Temperature).

Figure C4  Map of annual evapotranspiration deciles for the Perth region during the 2012–13 year

The total area-averaged evapotranspiration over the Perth region during the 2012–13 year was 643 mm compared to the long-term area-averaged evapotranspiration of 632 mm (based on the 1911–2012 period). Evapotranspiration was highest along the Darling escarpment ridge in the central to southern part of the region and lowest in the southeast (Figure C5).

Figure C5  Map of total annual evapotranspiration for the Perth region during the 2012–13 year

During the 2012–13 year, the entire Perth region experienced mean temperatures that were very much above the long-term average, based on the 1911–2013 period (Figure C6).

Figure C6  Map of annual mean temperature deciles for the Perth region during the 2012–13 year

Annual mean temperatures across the Perth region were generally above 16 °C. The western half of the region was warmer than the east (Figure C7).

Figure C7  Map of annual mean temperature for the Perth region during the 2012–13 year

Monthly mean temperatures for the Perth region were above the long-term average for most of the 2012–13 year (Figure C8). Monthly mean temperatures for four months of the year were above the 90th percentile. April 2013 was the warmest April on record for the Perth region, with area-averaged temperatures more than 3 °C above the long-term average.

Figure C8  Graph of monthly mean temperature for the Perth region during the 2012–13 year compared with the long-term average and percentiles for the region