The Engadine has two main seasons with a shoulder period between.
Winter (December to March) is the classic period for St. Moritz and the ski resorts. The snow is reliable, the light on the lake is extraordinary, and the valley runs at full capacity — which means full prices and full restaurants. The lake freezes thick enough for events from January. The Cresta Run operates November through February.
Summer (late June to September) brings hikers, cyclists, and the Bernina Express crowd. The glacier walks are accessible, the valley is warm by day (18–22°C) but cool at night, and the wildflowers on the high passes bloom in July. Sils Maria and the Fex Valley are best in summer. July and August are the peak months with corresponding pressure on accommodation.
Shoulder periods (April–May and October–November) are quiet. Some facilities close between seasons. The passes may still have snow in May; October brings autumn colour to the larch forests. Hotel rates drop significantly.
The Engadin Ski Marathon in March is one of the largest cross-country ski races in Europe, with 42,000 participants on the Engadine lakes — if you are here, plan around it.