Einsiedeln works in any season, but each has a distinct character. Summer (June to September) is for the Sihlsee, hiking, and the abbey at its most relaxed. The pilgrimage season peaks around September 14, the Feast of the Miraculous Dedication, when the square in front of the abbey fills with pilgrims from across Europe and the atmosphere is unlike anything you will find in an ordinary Swiss town.
Winter brings cross-country skiing on groomed tracks around the valley, and Hoch-Ybrig opens for downhill. Late December through January is ski jumping season — worth timing a visit around if the World Cup comes to the Schanzen. The town is also heavily decorated for Advent, with the nativity Diorama drawing its biggest crowds in the weeks before Christmas.
Spring and early autumn are quieter and arguably the most pleasant: mild weather, fewer pilgrimage groups, and good conditions for walking around the Sihlsee or up towards the Chatzenstrick pass.