Ærø is at its best from late May to early September, when the days are long, the ferries run frequently, and the cafes and small museums are open. July and August are the busiest months — book accommodation well in advance if you want to rent one of the old houses in Ærøskøbing.
Spring (late April–May) is quiet and the countryside is full of wildflowers and lambs. Autumn is golden and atmospheric but many of the smaller venues close from October. Winter is genuinely off-season — the island has fewer than 6,000 residents and outside of Ærøskøbing things can feel deserted, though the towns remain charming under a dusting of snow.
The Ærø Sailing Race (Ærø Rundt) in late July fills Marstal and Ærøskøbing harbours with classic wooden yachts and is one of the highlights of the local summer.