Weather in Sion

Find out what weather awaits you in Sion right now. In this section, we have collected up-to-date data, detailed charts, and a forecast for the near future so you can better plan your journey.

The climate of Sion can be characterized as cool and temperate, with a noticeable influence from its mountain location. There is no extreme heat here, and the air remains fresh throughout the year. Travellers planning a visit to this picturesque corner of Switzerland should note that even in the summer period, the weather is more conducive to active walks in comfortable clothing than seeking coolness in the shade.

Seasonality is quite distinct, but with a general tendency towards low temperatures. Winters here are truly cold: from December to March, thermometer readings consistently stay below zero, creating conditions for frosty weather. Summer arrives mild and restrained; in the warmest months — July and August — the air warms up only to a comfortable +13...+18°C, which is ideal for those who cannot tolerate sweltering heat.

An important feature of the weather in Sion is the high frequency of precipitation at any time of the year. The number of rainy or snowy days remains significant in both winter and summer, peaking in May and June (up to 20-21 days with precipitation). Therefore, when packing for your trip, be sure to bring a reliable umbrella, a raincoat, and waterproof shoes so that the whims of the weather do not stop you from enjoying your journey.

The temperature regime in Sion is characterized by distinct seasonality with fairly severe winters and moderately warm, fresh summers. The coldest month of the year is traditionally January, when the average temperature drops to -7.2°C. During this period, travellers should be prepared for serious frosts: night-time readings often reach -11.5°C, and even during the day, the air rarely warms up above -2.9°C. February and December support this winter trend, maintaining steady sub-zero temperatures, which creates the atmosphere of a true Alpine winter.

The summer season in the region brings long-awaited warming, however, one should not expect exhausting heat here. The warmest months — July and August — delight with comfortable average temperatures of around +13°C. During the day, the air usually warms up to a pleasant +18.4°C, creating ideal conditions for active walks and excursions without the risk of overheating. Nevertheless, even in summer, nights remain cool: the thermometer can drop to +7.5°C...+8.0°C, so you will need warm clothing even at the height of the holiday season.

Sion's climate is characterized by noticeable diurnal temperature fluctuations that can be traced throughout the year. The difference between daily highs and nightly lows averages about 10 degrees. For example, in May, with daytime temperatures of +10°C, the temperature at night falls almost to freezing, and in September, after a comfortable +14°C during the day, the air cools down to +3.9°C by night. When planning a trip, it is important to consider this feature and dress in layers to feel comfortable at any time of day.

Precipitation in Sion is distributed quite evenly throughout the year, however, its nature depends directly on seasonal temperatures. Since average thermometer readings drop below zero from November to March (down to -7.2°C in January), precipitation during this period falls mainly as snow. Winter here is quite snowy in terms of frequency: in December and January, 14 to 17 days with precipitation are recorded, creating the picturesque winter landscapes characteristic of Swiss regions.

The greatest number of days with precipitation occurs in late spring and early summer. May and June are the leaders in this regard: statistics indicate 20–21 days with precipitation per month. At this time, when temperatures rise to positive values, snowfalls are replaced by rain. Travellers should be prepared for frequent weather changes during this period and carry an umbrella or raincoat.

Despite the high frequency of wet days, the total volume of precipitation in Sion remains surprisingly stable and low — about 4–6 mm monthly. This suggests that heavy downpours or blizzards rarely happen here; rather, the city is characterized by light but frequent rain or light snowfall. The "driest" month in terms of inclement days can be considered February, but even then, precipitation falls on approximately 12 days of the month.

A trip to Sion requires a careful approach to your wardrobe, as the climate here is distinguished by coolness even in the warm months. In winter, when the temperature consistently stays below zero and can drop to -11°C, you vitally need quality thermal underwear, a thick down jacket, a warm hat, a scarf, and gloves. Given the high probability of precipitation and frost, choose insulated shoes with non-slip treaded soles to feel confident on snowy streets.

Summer in this region is quite fresh and rich in precipitation: even in July and August, the daytime temperature rarely exceeds 18°C, and there can be about twenty rainy days per month. Therefore, the principle of layering is more relevant here than ever: combine t-shirts with warm sweaters and fleece jackets that can be easily taken off or put on. Be sure to take a reliable umbrella, a raincoat, and a waterproof windbreaker, as rain is a frequent companion of travellers in Sion all year round.

For comfortable exploration of the city and its picturesque surroundings, comfortable trekking shoes or sturdy trainers suitable for long walks will be indispensable. Despite the often overcast weather and low temperatures, the mountain sun can be deceptive, so do not forget to pack sunglasses and cream with an SPF factor in your suitcase. Such a set of items will allow you to enjoy the beauty of Switzerland without being distracted by the caprices of the weather.