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Danger levels wind

Wind is the movement of air in the atmosphere, generally in a horizontal direction.

Wind is created as a result of differences in air pressure between air masses of varying temperature. The air moves from the higher air pressure (high-pressure area) to the lower air pressure (low-pressure area) until the air pressure is balanced out.

In Switzerland, westerly winds, cold north-easterly winds (called "bise") and southerly winds (called "foehn") are the most common types of wind occurring across widespread areas.

Danger level 5 (very severe danger)
Effects
  • Falling trees or entire groups of trees or sections of forest as well as electricity pylons and poles;
  • Severe damage to buildings;
  • Road, rail, water and air traffic disrupted or at a standstill;
  • Toppling of larger (empty) vehicles;
  • Securely anchored objects with a larger surface area, such as tents and scaffolding, as well as moveable objects such as garden furniture etc. can  be blown over;
  • High waves on lakes, which wash over the banks or shores
  • Electricity grid outages and/or failure of telephone networks for long periods of time and over widespread areas
Behaviour

Information on recommended action can be found here:  What to do during strong winds

Description of measurement and prognostic values
  • Top wind speeds in low to medium-altitude areas: > 140 km/h
  • Top wind speeds in higher-altitude areas (>1800 m above sea level): > 200 km/h
Danger level 4 (severe danger)
Effects
  • Falling trees;
  • Damage to individual buildings and roofs;
  • Disruption or restriction of road, rail, water and air traffic;
  • Movement  of securely anchored objects with a larger surface area, such as tents and scaffolding, as well as moveable objects such as garden furniture;
  • Electricity grid outages and/or failure of telephone networks
Behaviour Information on recommended action can be found here:  What to do during strong winds
Description of measurement and prognostic values
  • Top wind speeds in low to medium-altitude areas (incl. Foehn winds):  110-140 km/h
  • Top wind speeds in higher-altitude areas (>1800 m above sea level): 160-200 km/h
Danger level 3 (significant danger)
Effects
  • Falling branches and individual trees;
  • Damage to individual roofs;
  • Lightly anchored objects with larger surface areas, such as tents and scaffolding, can be blown over;
  • Some disruption to road, rail, water and air traffic;
  • Possible shutdown of ski lifts and cable cars.
Behaviour

Information on recommended action can be found here:  What to do during strong winds

Description of measurement and prognostic values
  • Top wind speeds in low to medium-altitude areas (incl. Foehn winds): 90-110 km/h
  • Top wind speeds in higher-altitude areas (>1800 m above sea level): 130-160 km/h
Danger level 2 (moderate danger)
Effects
  • Surface turbulence hinders light aircraft from flying;
  • Waves higher than usual on lakes;
  • Toppling of objects inadequately secured or free-standing objects;
  • Breaking of smaller branches
Behaviour Information on recommended action can be found here:  What to do during strong winds

Description of measurement and prognostic values

  • Stormy winds in low and medium-altitude areas (incl. Foehn winds): 70-90 km/h

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