Snow is the most common form of solid precipitation and consists of many very small ice crystals. These form at temperatures below -4 °C, and fall to earth, as long as their falling speed and the temperature and humidity below the clouds do not allow the crystals to melt or evaporate.
Danger levels snow
Danger level 1 (minimal or no danger)
Snowfall warnings are issued in levels 2 - 5.
Danger level 2 (moderate danger)
Impact
Slippery conditions due to snow-covered roads.
Recommended action
Information on recommended action can be found here: What to do during snowfall
Description of measurement and prognostic values
- Snowfall in lowland areas of German-speaking Switzerland: 10-15 cm/24h; 20-35 cm/48h; 30-50 cm/72h
- Snowfall in lowlands of Western Switzerland and south of the Alps: 8-12 cm/24h; 20-35 cm/48h; 30-50 cm/72h
- Snowfall in the mountains: 20-40 cm/24h; 35-70 cm/48h; 50-100 cm/72h
Danger level 3 (significant danger)
Impact
- Worsening of road condition.
- Disruption to air and rail travel.
- Branches breaking due to snowload.
Recommended action
Information on recommended action can be found here: What to do during snowfall
Description of measurement and prognostic values
- Heavy/intensive snowfall in lowland areas of German-speaking Switzerland: 15-30 cm/24h; 35-50 cm/48h; 50-70 cm/72h
- Heavy/intensive snowfall in lowlands of Western Switzerland and south of the Alps: 12-30 cm/24h; 35-50 cm/48h; 50-70 cm/72h
- Heavy/intensive snowfall in the mountains: 40-60 cm/24h; 70-100 cm/48h; 100-130 cm/72h
Danger level 4 (severe danger)
Impact
- Impassable sections of road.
- Disruption to air and rail travel.
- Falling branches or trees as a result of the weight of their snowload.
- Interruption of electricity supply and/or telephone network, particularly in regions that are not easily accessible.
- Heavy snowload on roofs.
Recommended action
Information on recommended action can be found here: What to do during snowfall
Description of measurement and prognostic values
- Heavy/intensive snowfall in lowland areas of German-speaking Switzerland: 30-50 cm/24h; 50-70 cm/48h; 70-90 cm/72h
- Heavy/intensive snowfall in lowlands of Western Switzerland and south of the Alps: 30-50 cm/24h; 50-70 cm/48h; 70-90 cm/72h
- Heavy/intensive snowfall in the mountains: 60-90 cm/24h; 100-140 cm/48h; 130-180 cm/72h
Danger level 5 (very severe danger)
Impact
- Road and air traffic is brought to a standstill.
- Massive disruption to rail transport.
- Falling branches or trees as a result of the weight of their snowload.
- Heavy snowload on roofs.
- Breakdown of electricity supply and telephone communications network.
Recommended action
Information on recommended action can be found here: What to do during snowfall
Description of measurement and prognostic values
- Heavy/intensive snowfall in lowland areas of German-speaking Switzerland: >50 cm/24h; >70 cm/48h; >90 cm/72h
- Heavy/intensive snowfall in lowlands of Western Switzerland and south of the Alps: >50 cm/24h; >70 cm/48h; >90 cm/72h
- Heavy/intensive snowfall in the mountains: >90 cm/24h; >140 cm/48h; >180 cm/72h
Notes:
The snowfall warnings are primarily issued for widespread precipitation.
The warning threshold values in category 2 and 3 for lowland areas differ according to region.