The Bay of Islands has a subtropical climate — warm and wet in summer, mild and damp in winter. Peak season is December through February, when sea temperatures climb to 22°C and the bay fills with cruising yachts. Booking accommodation and boat trips well in advance is essential during the Christmas-New Year period and at Waitangi Day on 6 February.
Shoulder seasons — March-April and October-November — are arguably the best time to visit. The weather is still reliably good, dolphin sightings are common, and prices drop. Winter (June to August) is quiet, with shorter days and occasional storms; some operators run reduced schedules but the bay is still walkable and the historic sites are open. The Bay of Islands Sailing Week in late January is one of the biggest yacht-racing events in the southern hemisphere.