Summer (June to August) is the obvious season for the beaches, with long days, water that reaches 20°C in August, and Wilhelmine seafronts at their best. The trade-off is crowds: July and August can feel oversubscribed at Binz and the Königsstuhl.
May and September are the sweet spot — the chalk cliffs are at their photogenic best in the slanting light, the beaches are accessible without crowds, and the prices are lower. Late autumn brings dramatic Baltic storms that wash chunks off the cliffs and make for atmospheric walking. Winter is cold, wet, and the seaside towns mostly close down, but the forest and coastal paths have a stark beauty.