WA’s capital city of Perth is bathed in sunshine for an average of nine hours a day, with a total of 131 perfect blue-sky days every year. That officially makes it the sunniest capital city in Australia, with one of the most enviable outdoor lifestyles in the world.
Perth’s average maximum summer temperature is 29°C, and February is generally the hottest month. Temperatures hover around 12°C in winter (June to August).

SOUTH WEST WEATHER

The South West region has a slightly cooler, milder climate than Perth itself.
The western coastline between Bunbury and Augusta is slightly warmer than the southern coastline from Augusta to Albany, due to the Antartic currents that flow along this coastline. During Winter the southern coastline can be quite wild and wet.
Inland, around Nannup, Bridgetown and Mt Barker, the temperature can fluctuate significantly more than along the coast. The inland areas generally experience more rainfall and lower temperatures overnight with frost quite common during certain times of the year (late Winter and Spring).
In general, the weather pattern has 4 distinct seasons:
Summer – usually running from Dec-Feb, when temperatures along the coast ranges between 25 and 35°C during the day and 15-20°C overnight. There is generally little chance of rain during these months. The countryside around this time of the year (particularly late Summer) can become quite dry and brown due to the lack of rain. Along the western coastline, easterly winds are prevalent in the morning followed by stronger sea breezes in the afternoon.
Autumn – Mar-May, is one of the best times of the year. Usually from mid-March the temperatures can start to fall slightly but the days are still (generally) warm and mild with blue skies. There may be occasional light rainfall which puts some green back into he paddocks, and deciduous trees start to change colour and lose their leaves. The surf at this time of year is also usually at its biggest.
Winter – Jun-Aug. During the day the temperature may range from 12-18°C, and overnight 5-10°C, and generally cooler inland at night. It is rare for the temperature to drop to zero except if some higher regions like the Perongerups where it can experience light snow. Daylight hours exist for about 10 hours a day in Winter.
Spring – Sep-Nov sees the countryside at it’s best, with paddocks green, vineyards looking their most beautiful, but the beaches and coast itself can often be hit by strong sea surges and storms making them wild and somewhat less appealing for beach goers. You can get some rain throughout Spring but you can also get some stunning blue-sky days with temps 17-20°C and just idyllic.

Useful Information:

For daily weather and weekly forecast, visit http://www.weatherzone.com.au/wa/southwest
For climate averages, extremes and records for the South West and specific townships, visit http://www.weatherzone.com.au/climate/stationdrill.jsp
For sunrise and sunset times and moon phases, visit http://www.timeanddate.com/astronomy/