April–May and September–October. Not the high season.
Trade winds are steady from April through October; waves are small and swimmable at Waikīkī year-round. The peak visitor windows — Christmas–New Year, spring break, and the last two weeks of July — triple hotel rates without improving the weather. If you have flexibility, early May or late September gives the best ratio of price to conditions. Humpback whale season runs December through April, visible from shore off the Ko Olina side; big-wave North Shore season overlaps November through February.

