Sneek's high season is summer, when the lakes fill with sailors and the town hosts the Sneekweek regatta in the first week of August — the largest sailing event on inland waters in Europe and a riotous week of racing, music and drinking. If you want the town quiet, come in May, June or September.
Winter has its own draw: when the canals and lakes freeze hard enough — increasingly rare — the Elfstedentocht ice skating route runs through Sneek, and the town turns out in force. Outside these moments, late autumn and winter are quiet and bleak; expect short days and a lot of wind.