Bunbury has a Mediterranean climate — warm, dry summers and mild, wet winters. The best time to visit for outdoor activities, beach swimming, and dolphin encounters is from October through April, when the weather is reliably warm and the sea is calm. Summer temperatures typically reach 28–32°C.
The dolphin encounters at Koombana Bay are possible year-round, but calm summer mornings tend to bring the dolphins closer to shore. The diving and snorkelling season at the offshore reefs runs from spring through autumn.
Winter (June–August) is mild by Australian standards — rarely cold — and the lower tourist numbers mean quieter beaches and easier accommodation. The Tuart Forest is worth visiting year-round, though spring brings wildflowers and the best birdwatching.