In general, you'll find blue skies, tepid days, breezy nights and customary weather. September to November is the spring and the wildflowers are out in Australia, which makes it an excellent time to visit. Summer is from December to February and weather is hot. The hottest months are January and February.
The universal accord is that the months connecting the winter and spring seasons are the best time to visit Perth due to the balance of comfortably gentle weather. In order to travel to Perth from overseas, the end of August to the end of March would be suitable annually. Winter months are from June to August.