The whale season — July to October — is the main driver of visitor timing. July and August are the peak months: the greatest number of whales, the most activity with calves, and the longest days. This is also when prices peak and accommodation needs booking well ahead.
Outside whale season, the islands are quieter and cheaper. May and June have the most reliable sailing conditions. November to April is the cyclone season — Tonga is occasionally hit by tropical cyclones, and travel insurance with evacuation cover is advisable. The shoulder periods (May–June and November) have good weather, fewer visitors, and lower prices.
Year-round, temperatures are warm: 26–30°C in the dry season, slightly higher and more humid in the wet season. The water temperature stays above 24°C throughout the year, making wetsuits optional for most swimmers except during whale dives where they provide protection rather than warmth.