Jacmel's carnival runs in the weeks before Lent and culminates on the Sunday before Mardi Gras. It is widely considered the most artistically rich carnival in Haiti, drawing on the town's papier-mâché tradition for the elaborate masks and full-body costumes that lead the parade through the historic centre.
If you can plan a trip around it, do — the town is at its best, and the costumes are extraordinary. Book accommodation well in advance; prices roughly double during carnival week and the small hotels in the centre sell out months ahead.