Perth enjoys a Mediterranean climate like Southern California, averaging eight hours of sunshine a day, all year round. The average maximum summer temperature is 31C (88F) and 19C (66F) in winter.
The seasons in Perth are the opposite to those in the northern hemisphere - so Christmas "down under" means beach weather, seafood and barbecues. Plus, due to the huge size of Western Australia, the climate is diverse. Being in the South West of Western Australia, Perth experiences warm dry summers and cool wet winters, whilst the northern area of WA enjoys tropical summers and dry warm winters.
For more information about Perth's weather see the Bureau of Meteorology website.