Climatology

The Vaud Alps region covers an area of approximately 700 km², with elevations ranging from 372 meters (Lake Geneva) to 3,210 meters (the summit of the Diablerets). Due to its location, this region is exposed to humid air masses from the West to the North, much like the entire northern side of the Alps, giving it a humid and cool climate compared to the more sheltered and sunnier inner Alps, such as the central Valais.

The average annual temperatures calculated for the period 1981-2010 range from 10 to 11°C along the shores of Lake Geneva and in the Rhône Valley in the Chablais, 3°C at 2,000 meters above sea level, and -3°C at 3,000 meters above sea level. The average monthly temperatures vary from 1.5°C in the coldest month (January) to 20°C in the warmest month (July) at low altitudes. At high altitudes, at 3,000 meters above sea level, temperatures range between -8.5°C and +4°C. Permafrost is present year-round on the highest peaks of the Vaud Alps. Valley bottoms can favor the accumulation of cold air, which influences average temperatures, especially in the colder season.

Precipitation also varies greatly depending on regional and local topography in the Vaud Alps. On average, 1,000 to 1,300 mm of precipitation fall annually in areas along the shores of Lake Geneva and in the Rhône Valley in the Chablais, whereas precipitation reaches around 2,400 mm per year on the peaks exposed at 3,000 meters above sea level. The precipitation regime is semi-continental, with higher rainfall typically occurring during the warm season (thunderstorms).

(Written in collaboration with Prof. Jean-Michel Fallot)