May to August is the high season and the only time the full programme of boat trips runs from the Scottish Seabird Centre. The gannet colony on the Bass Rock is at its loudest and most active from May through July; puffin watching at Craigleith and Fidra peaks in June. The Fringe by the Sea festival in early August brings a week of music and literary events to the town.
September and early October are still warm enough for the beaches and far quieter — the breeding seabirds have gone but the place itself is at its best.
Winter is bracing, beautiful, and almost empty. Many boat trips stop running. The walks (Law, Tantallon, John Muir Way) are all still open and dramatic in winter light. Pack waterproofs and accept that the wind may stop play.