The Dolomites divide into two main seasons, with shoulder periods in between when the lifts are neither running for skiing nor fully open for summer hiking.
Winter (December–March) is ski season. Snow is reliable above 1,500 metres from mid-December; the busiest weeks are Christmas, New Year, and mid-February school holidays. January is the quietest winter month, often with excellent snow and fewer crowds. Temperatures at altitude can drop to -15°C; at valley level, cold but clear days are common.
Spring (April–May) is the awkward in-between: ski lifts closing but hiking trails still under snow above 1,600 metres. Some years the high passes don't clear until mid-June. This is the least appealing time to visit.
Summer (June–September) is the peak hiking and via ferrata season. June is often the nicest month — the wildflowers are at their best, the trails are clear, and the Italians haven't arrived yet in force. July and August are crowded around the main attractions; September is excellent, with stable weather, golden light, and the first autumn colours on the valley floors.
Autumn (October–November) brings snow above 1,800 metres, but the valley towns are empty and the light on the pale rock is exceptional. This is when you get the mountains largely to yourself.
Thunderstorms are common on summer afternoons; always start mountain walks early and be back at the rifugio by early afternoon.