Contents area

Explanation of the danger levels

The 5 danger levels.


Top bar Navigation

Swiss federal authoritiesSwiss federal authorities

The hazard categories numbered 1 to 5 have been determined by the specialist government bodies for natural hazards. Prevailing circumstances are outlined in terms of their potential dangers and their impact on society for each individual category within the various natural hazard types. Whilst the definitions have been made as similar as possible for the same hazard category numbers across the different natural hazards, it is, of course, not possible to make direct comparisons between them. Detailed explanations of the hazard categories for each natural hazard can be found here.

Natural Hazards



Earthquakes are caused by a sudden release of stress along faults in the crust.



Ground frost occurs when the temperature close to the ground (measured 5 cm above the natural ground level) falls below the freezing point.



A thunderstorm is a complex meteorological event, characterised by the presence of electrical discharges (lightning) followed by thunder. The conditions needed for a thunderstorm to develop are a sufficient level of humidity and the rapid upward movement of air, e.g. as a result of being warmed. Inside a storm cloud (cumulonimbus) there are often strong updrafts and downdrafts, which cause turbulence. Hazardous weather events that can occur in a thunderstorm include lightning, heavy precipitation (downpour of rain, hail, graupel/snow pellets, and, in winter, snow) as well as wind gusts that can sometimes reach up to hurricane strength.



Our perception of heat is affected by the following meteorological parameters: air temperature, radiation from the sun, relative air humidity, and wind.



Hochwasser ist ein Zustand, bei welchem Gebiete, die normalerweise im Trockenen liegen, von Wasser überflutet werden.



Avalanches rank among the greatest natural hazards in the Alpine region. They can affect houses, settlements and transportation routes, as well as people engaging in winter sports.


Mass movements

Landslides - Debris flows - Rockfalls



Rain is the most common form of liquid precipitation from clouds, and develops as a result of small, suspended cloud droplets growing into larger drops of water, which then fall to earth because of their weight



Snow is the most common form of solid precipitation and consists of many very small ice crystals.


Slippery roads

Ice on the roads develops as a result of cold and wet conditions.


Forest fire

Given that only 10 percent of forest fires have a natural cause (lightning), it can be assumed that 90 percent of such fires are caused by inappropriate human behaviour (discarding glowing cigarette butts, barbecue fires that are not completely extinguished etc.).



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