Lake Geneva's winds: bise, joran, vaudaire, séchard and the others
Updated 17.10.2026
General winds, thunderstorm winds and breezes: recognising the lake's winds, where they blow and what they foretell.
Three families of winds
Lake Geneva's winds fall into three families: general winds (the bise, the westerly), thunderstorm winds and breezes (thermal winds). Everywhere, the steep relief of the shores speeds them up: a wind can hit the lake with sudden violence. The same wind sometimes changes name from one basin to the next, and several local winds exist only in one corner of the lake.
General winds
Linked to large-scale weather patterns, they blow over much of the lake and can last several days.
The Bise
The most frequent wind, a fair-weather wind, cold and dry; once established, it blows in continuous gusts, often for several days (SISL, ASL).
Named by the app on: Petit Lac, Grand Lac, Haut Lac.
The Vent
Strong wind from south-south-west to west, linked to passing depressions; it heralds bad weather, with heavy clouds over Geneva and the Jura. On the Haut Lac, the mountains deflect it into eddies (SISL).
Named by the app on: Petit Lac, Grand Lac, Haut Lac.
Thunderstorm winds
Sudden, violent, often brief: these are the ones that catch sailors out.
The Joran
Comes down abruptly off the Jura, especially in stormy or rainy weather, often heralded by big black cumulus clouds over the Jura; strong gusts at first, then it steadies, and the temperature drops (SISL).
Named by the app on: Petit Lac, Grand Lac.
The Vaudaire
Strong wind from the south-east on the Haut Lac, from south-east to east on the Grand Lac, feared for its suddenness and strength, heightened by the corridor of the Rhône plain; a short-lived summer wind, often born of thunderstorms (SISL).
Named by the app on: Haut Lac, Grand Lac.
The Bornan
A southerly thunderstorm wind, coming down from the mountains of the Savoy hinterland in very violent, sudden gusts, especially in hot weather; its effects are felt mainly between Rolle and Lutry (SISL).
Named by the app on: Grand Lac.
The Môlan
The Petit Lac's equivalent of the bornan: a southerly thunderstorm wind, coming down from the mountains in gusts (SISL).
Named by the app on: Petit Lac.
Breezes
Light thermal winds that only exist when no major wind is blowing.
The Séchard
A light north-easterly, a thermal breeze; it covers the whole lake except the Haut-Lac, where it is unknown (SISL, ASL).
Named by the app on: Petit Lac, Grand Lac.
The Rebat
A daytime breeze that blows opposite to the night wind (rebat of the morget, the vaudaire or the bise); channelled by the relief, it runs along the shore until late afternoon (SISL).
Named by the app on: Petit Lac, Grand Lac, Haut Lac.
The Morget
A light night breeze, channelled by the valleys; it speeds up over steep slopes before dispersing (SISL).
Named by the app on: Grand Lac.
Other winds the app doesn't name
- The bise noire: an autumn and winter wind from the north, gusty, under a low cloud ceiling and in dim light.
- The vent blanc: a summer wind, warm and steady, in sunny weather; confined to the Petit Lac, it can extend to the Grand Lac, very rarely to the Haut Lac.
- The maurabia: a summer wind under almost clear skies, a herald of bad weather; steady, it raises fine breaking waves.
- Night breezes: light, channelled by the valleys, they speed up over steep slopes before fanning out — the morget, the bisoton, the dézaley, the jaman, the vauderon, the albrans, the birran, the molaine, the fraidieu, the jorasson.
Based on the SISL technical dossier. The Association pour la sauvegarde du Léman notes that these local breezes, once regular, are now disrupted by urbanisation and warming.
How the app names the wind
The “Named winds of Lake Geneva” map layer (Wind and weather menu) reads the forecast wind hour by hour in each basin and names it from its direction, strength, basin and time of day; when a station measures the wind close by, its gusts confirm a joran or a vaudaire, or not. The rebat, for its part, is recognised by blowing opposite to the previous night's wind. A name is a reading, not a measurement: two regimes can compete for the lake, and the app says so.
See also
The Winds and weather guide, plus: Thunderstorms and storm warnings, Reading the lake weather.