New Caledonia has two main seasons. The dry, cool season runs from May to October; the hot, wet season from November to April.
Best time: May to October. Temperatures are comfortable (20-26°C), humidity is lower, and rainfall is modest. This is the best season for hiking, diving, and general exploration. July and August are peak travel months for Australians and New Zealanders — book accommodation and domestic flights early. The whale-watching season runs from mid-June to mid-September, when humpback whales come into the lagoon to calve.
October and November are a pleasant shoulder period — warm but not oppressively humid, with manageable crowds.
December to April is hotter (regularly above 30°C), more humid, and brings the risk of tropical cyclones, particularly from February onwards. Heavy rain can make road travel difficult, especially on the east coast. That said, the lagoon is extremely warm for swimming and the landscape is at its greenest.
Avoid if possible: The Australian and New Zealand school holidays in December-January, and the French holiday period in July-August, push up prices and fill up the islands. If visiting during peak months, budget accordingly and book ahead.