Heilala Festival (July)
Tonga's biggest annual celebration, held around the King's Birthday in early July. The festival runs for about a week in Nuku'alofa and includes brass band competitions, traditional dance performances, singing contests, and the Miss Heilala beauty pageant — a prestigious event in Tongan society. There are parades through the capital and various community events. If you're passing through Tongatapu in early July, it's a good reason to linger.
Constitution Day (4 November)
Marks the signing of Tonga's constitution in 1875. A public holiday with some ceremonies, though less tourist-visible than the Heilala Festival.
Emancipation Day (4 June)
Commemorates the freeing of serfs in 1862 under King Tupou I. Public holiday.
Christmas and Easter
Tonga is a deeply Christian country and both holidays are observed seriously. Churches hold major services, and family gatherings with feasting are the norm. Not much happens commercially — plan on most things being closed over Christmas Day and Good Friday.
Agricultural Shows
Village and island-level agricultural shows take place periodically, with displays of produce, craft, and traditional skills. These are low-key community events rather than tourist spectacles, but they offer a genuine window into Tongan rural life if you happen to be in the right place at the right time.