The climate of Switzerland is primarily the result of the country’s geographical location in the mid-northern latitudes of central Europe, along with its complex topography of high Alpine peaks and deep valleys. The geographical positioning determines the solar radiation over the year, and thus the seasons and the day lengths. The local weather conditions, on the other hand, are dependent on both the geographical location and the season. The varied topography of the Alpine region makes for regional differences in weather. There are also regular features of the climate that are peculiar to Switzerland (Regularly occurring weather conditions), such as the cold spell in June known as the “Schafskälte” or the spate of frost days which occurs in May, known as “Eisheiligen”.
The climate of central and northern Europe, including Switzerland, is heavily influenced by the Atlantic Ocean. Switzerland is located in the West Wind Zone, which is why for most of the year air masses arrive in Switzerland from the west, whereas air currents from easterly, northerly and southerly directions are comparatively rare. High or low pressure systems centred directly over Switzerland are also comparatively rare (2% of the direction of the air currents, which amounts to around one week per year).
On prevailing currents from westerly and northwesterly directions, mild, humid sea air travels across Switzerland. These have a cooling effect in the summer, and a warming effect in winter. In the summer, when the strong, westerly high-altitude winds (the jetstream) move further north, as they normally do, Switzerland is dominated by a continental climate with a distinct diurnal cycle in temperature and precipitation. During this season precipitation often falls in the form of thunderstorms in the latter half of the day. Over the course of a year, most areas in Switzerland receive sufficient precipitation to meet the needs of industry and the population. 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. The south side of the Alps is also known for its heavy precipitation in conjunction with low-pressure systems in the Gulf of Genoa, and when moist air masses move up over the southern Alps during southwesterly flow or southerly Foehn conditions..