Rottnest Island has a temperate Mediterranean style climate with wet-mild winters and dry summers. The island is slightly cooler than the nearby city of Perth.
Summer: Summer falls during the months of December to March and the temperature ranges from 30 degree Celsius on average to 40 degree Celsius at the height of summer. Humidity is minimal.
Autumn: April to May is a good time to visit for those who might find the beaches too hot in the summer months. The temperatures start cooling from the month of April, with an average high of 25 degree Celsius and an average low of 13 degree Celsius.
Winter: The winter months of June to August is when it really rains, and the seas turn too rough for swimming. Average temperatures range from 19 degree Celsius to 7 degree Celsius. However, temperatures have been known to drop below 0 degree Celsius on clear nights.
Spring: Spring temperatures range between 20 degree Celsius to 11 degree Celsius and the most pleasant months are October and November.
The best time to visit Rottnest Island is in Autumn or Spring. The months of October and November are particularly recommended as the weather is perfect and the seas calm enough for a swim or water sports.