Switzerland's climate is heavily influenced by the Alps as well as by the Atlantic Ocean. Winters in the northern plateau are mild and damp, whereas higher altitudes experience arctic temperatures. At altitudes above 1200-1500 metres or so, precipitation in the winter falls mainly as snow. The south side of the Alps is strongly affected by the Mediterranean Sea, and so winters there are mild and the summers warm and humid, and sometimes hot. All along the Alpine ridge there are frequent thunderstorms in the summer.
The Climate of Switzerland
Climate can be defined as the totality of typical weather processes in a region over a given period of time. The climatic portrait of Switzerland is formed mainly as a result of the geographical position of the country and its complex topography. The geographical location determines what kinds of weather are predominant, while the topography gives rise to regional differences and special climatic conditions within Switzerland.
Climate portrait of Switzerland
The climate of Switzerland is heavily influenced by the Atlantic Ocean. On prevailing currents from westerly and northwesterly directions, mild, humid sea air ends up in Switzerland. In summer, this has a cooling effect, and in winter a warming effect, and most areas enjoy an adequate amount of precipitation throughout the year. The Alps act as a prominent climatic barrier between northern and southern Switzerland.
Southern Switzerland is mainly affected by the Mediterranean Sea, where the climate differs from that of the north, most notably in its significantly milder winters.
Further information on weather events of the past and on Switzerland's climate:
Dry in the inner Alpine valleys
In addition to their prominent role as a climate barrier between north and south, the Alps also generate several different climate regions. One of these is that of the inner Alpine valleys, which have a distinct climate of their own as they are shielded from precipitation from both the north and the south. The consequence of this is the relatively dry conditions throughout the year.
Typical examples of these dry valleys are the Canton of Valais in the south west and the Engadine in the south-east of Switzerland. In the Valais, the average precipitation is between 500 and 600 mm per year, depending on the particular area, while in the Engadine it is between 600 and 700 mm per year. In contrast, the northern Alpine foothills, the Alps and southern Switzerland, annual precipitation volumes of around 2000 mm are the norm. In the northern plateau, the average amount is around 1000 to 1500 mm per year. Around double the amount falls in summer compared to in winter.
Further information on precipitation distribution in Switzerland:
Snow in winter
Starting at an altitude of 1200-1500 m above sea level, precipitation during winter predominantly falls as snow, such that the area is often covered by a solid layer of snow for weeks, and even months at higher altitudes. Snowfall is relatively rare in the low-lying areas of western Switzerland (greater Geneva area) and northern Switzerland (greater Basel area) as well as in the lowland in the southern tip of Switzerland. In these warmer regions - mainly because of their low elevation - completely snow-free winters are not uncommon.
From Arctic to Mediterranean
Foehn wind is a special feature of Swiss climate. This wind that crosses the Alps creates distinctly mild and dry conditions on the leeward, downwind side, as well as frequently high wind speeds. There is a northern foehn and a southern foehn. The southern foehn gives rise to warm conditions on the north side of the Alps, and occurs primarily between autumn and spring. The most significant effects of the foehn are seen in the north-south aligned foehn valleys, e.g. in the Reuss and Rhine valleys. The northern foehn is a major climate factor for southern Switzerland during the winter months. It often gives rise to good weather and mild conditions lasting several days in Ticino.
Under the fog
Fog is a very common occurrence in the cold months of the year. From late autumn through to spring, low-lying fog regularly forms, predominantly in high pressure areas. This tends to occur mostly along rivers and lakes as the air above these is very damp. The cooling of the air then causes local condensation.
High fog is often found in conjunction with the wind known as Bise. Bise is a cool, dry east and north-east wind. The dry air of the Bise causes low-lying fog to rise, and often, the stronger the Bise, the higher the upper border of the fog layer will be. Strong, persistent Bise wind can mean that the high fog does not disappear for several days or even weeks. The northern part of central Switzerland and the southern foot of the Jura are particularly affected by this phenomenon. As a result of high fog, we see inversions, meaning that in the Alps, for example, the air is warmer above the fog layer than below it.
Recurrent peculiarities of the Swiss climate
Besides Foehn and fog, the climate of Switzerland has numerous other peculiarities that occur more or less regularly - from snowfalls in spring to the cloud-covered start of July to the Indian summer in autumn.
The average climate of Switzerland
To enable us to describe the climate, we use average values, taken from many years' worth of measurements, of various meteorological parameters such as temperature, precipitation and hours of sunshine. The averages are calculated globally for the same period of 30 years, so that the climates of different regions can be compared with one another. Average values from these so-called normals periods are also known as climate normals.
The average condition of the climate described using climate normals is a statistical parameter around which the actual conditions fluctuate.