Other facts from our historical weather data: Which is the warmest month in Perth? July has an average maximum temperature of 20°C (68°F) and is the warmest month of the year. Which is the coldest month in Perth? The coldest month is December with an average maximum temperature of 7°C (45°F). Which is the wettest month in Perth? October tops the wettest month list with 103mm (4.1 in) of rainfall. Which is the driest month in Perth? April is the driest month with 71mm (2.8 in) of precipitation. Which is the sunniest month in Perth? May is the sunniest month with an average of 193 hours of sunshine. No idea where to travel to this year? We have a tool that recommends destinations based on your ideal conditions. Find out where to go with our weather planner.