Switzerland works in two distinct tourist seasons: summer (June–August) and winter (December–March). Both are peak periods for different reasons, and both come with peak prices and crowds. The shoulder seasons — May and September/October — offer the best balance of decent weather, open facilities, and fewer visitors.
Summer (June–August) is the most popular time for hiking, cycling, lake swimming, and exploring cities. Alpine trails are snow-free, mountain railways are fully operational, and daylight extends past 9pm. July and August are busy: book accommodation in advance, especially in resort towns and around the Jungfrau region. Expect afternoon thunderstorms in the mountains — standard summer weather in the Alps.
Autumn (September–October) is arguably the most rewarding time to visit. Temperatures are comfortable, the summer crowds have thinned, and the foliage at lower elevations turns a deep amber. High mountain trails start closing from mid-October onwards as snow returns.
Winter (December–March) means skiing. The resorts at Zermatt, Verbier, Davos, Klosters, and St. Moritz are world-class and attract a well-heeled international crowd. Prices in ski areas are very high in January and February. Christmas markets in Zurich, Bern, and Basel are charming from late November through December.
Spring (March–May) is the weakest season. Many mountain lifts close during the muddy period between ski season and summer hiking. At lower elevations — particularly in Ticino and around the lakes — spring arrives early and can be pleasant from April. Higher up, patience is required until late May.
In general: come in June, September, or early October if you want the Alps without the peak-season crush.