Rain - MeteoSwiss

Quick links (Access keys)

Rain

Rain is the most common form of liquid precipitation. It develops as a result of small, suspend-ed cloud droplets growing into larger drops of water, which then fall to earth because of their weight.

Swiss federal authorities

MeteoSwiss

Federal Office of Meteorology and
Climatology MeteoSwiss

Hazard category 5 (very severe hazard)

Possible impacts	Extreme rise in the water level of streams and lakes Flooding in many areas Failure of drainage and sewer systems and flood protection barriers Flooding of underpasses, underground garages and cellars/basements Massive disruption to bus and rail traffic (delays and cancellations) Massive disruption to road traffic (longer journey times, risk of accidents, road closures) due to wet roads, poor visibility and flooding) High likelihood of landslides on sloping terrain and mudslides
Description of measurement and prognostic values	Sustained rainfall north of the Alps and in the Alps: >120 mm/24h; >150 mm/48h; >170 mm/72h Sustained rainfall south of the Alps and in Simplon: >160 mm/24h; >200 mm/48h; >240 mm/72 h Sustained rainfall in Verbano, Valle Maggia: >250 mm/24h; >300 mm/48h; > 350 mm/72h

Possible impacts

Extreme rise in the water level of streams and lakes
Flooding in many areas
Failure of drainage and sewer systems and flood protection barriers
Flooding of underpasses, underground garages and cellars/basements
Massive disruption to bus and rail traffic (delays and cancellations)
Massive disruption to road traffic (longer journey times, risk of accidents, road closures) due to wet roads, poor visibility and flooding)
High likelihood of landslides on sloping terrain and mudslides

Description of measurement and prognostic values

Sustained rainfall north of the Alps and in the Alps: >120 mm/24h; >150 mm/48h; >170 mm/72h
Sustained rainfall south of the Alps and in Simplon: >160 mm/24h; >200 mm/48h; >240 mm/72 h
Sustained rainfall in Verbano, Valle Maggia: >250 mm/24h; >300 mm/48h; > 350 mm/72h

Hazard category 4 (severe hazard)

Possible impacts	Potential for rivers to overflow onto floodplains and flood zones as well as around lake shores Heavy and rapid rise in the water level of streams and lakes Potential for localized landslides on steeply sloping terrain Potential for failure of drainage and sewer systems Flooding of underpasses, underground garages and cellars/basements Limitations to bus and rail traffic (delays and cancellations) Limitations to road traffic (longer journey times, risk of accidents, road closures) due to wet roads, poor visibility and flooding)
Description of measurement and prognostic values	Sustained rainfall north of the Alps and in the Alps: 80-120 mm/24h; 110-150 mm/48h; 130-170 mm 72h Sustained rainfall south of the Alps and in Simplon: 130-160 mm/24h; 160-200 mm/48h; 200-240 mm/72h Sustained rainfall in Verbano, Valle Maggia: 200-250 mm/24h; 250-300 mm/48h; 300-350 mm/72h

Possible impacts

Potential for rivers to overflow onto floodplains and flood zones as well as around lake shores
Heavy and rapid rise in the water level of streams and lakes
Potential for localized landslides on steeply sloping terrain
Potential for failure of drainage and sewer systems
Flooding of underpasses, underground garages and cellars/basements
Limitations to bus and rail traffic (delays and cancellations)
Limitations to road traffic (longer journey times, risk of accidents, road closures) due to wet roads, poor visibility and flooding)

Description of measurement and prognostic values

Sustained rainfall north of the Alps and in the Alps: 80-120 mm/24h; 110-150 mm/48h; 130-170 mm 72h
Sustained rainfall south of the Alps and in Simplon: 130-160 mm/24h; 160-200 mm/48h; 200-240 mm/72h
Sustained rainfall in Verbano, Valle Maggia: 200-250 mm/24h; 250-300 mm/48h; 300-350 mm/72h

Hazard category 3 (significant hazard)

Possible impacts	Rise in the water level of streams and normally dry ditches Limitations to road traffic (longer jorney times, risk of accidents) due to poor visibility and flooding Localized flooding of underpasses, underground garages and cellars/basements possible Potential for localized landslides on steeply sloping terrain
Description of measurement and prognostic values	Sustained rainfall north of the Alps and in the Alps: 50-80 mm/24h; 80-110 mm/48h; 100-130 mm/72h Sustained rainfall south of the Alps and in Simplon: 100-130 mm/24h; 130-160 mm/48h; 160-200 mm/72h Sustained rainfall in Verbano, Valle Maggia: 150-200 mm/24h; 200-250 mm/48h; 250-300 mm/72h

Hazard category 2 (moderate hazard)

Possible impacts	Local swelling of streams possible in areas where the ground is already saturated In exceptional cases local flooding, i.e. of underpasses, underground garages and cellars/basements
Description of measurement and prognostic values	Sustained rainfall north of the Alps and in the Alps: 30-50 mm/24h; 50-80/48h; 60-100 mm/72h Sustained rainfall south of the Alps and in Simplon: 70-100 mm/24h; 100-130 mm/48h; 130-160 mm/72h Sustained rainfall in Verbano, Valle Maggia: 100-150 mm/24h; 150-200 mm/48h; 190-250 mm/72h

Recommendations for action

What to do in the event of heavy rainfall

Notes

These warnings are primarily used for widespread precipitation (also potentially in combination with a thunderstorm in the summer).

Please note: the warning threshold values differ for north and south of the Alps within the same warning category!

Description Warning thresholds (PDF, 756.3 kB)

About us

MeteoSwiss is the Federal Office for Meteorology and Climatology. We keep our finger on the pulse of the weather and climate, so it’s all clear as day to you.

Stay informed

Twitter
YouTube
Instagram
Vimeo
LinkedIn

Additional Information

Contact
Working at MeteoSwiss
MeteoSchweiz-Blog
About us
A-Z of weather and climate
Service

Quick links (Access keys)

Contents area

Top bar Navigation

Service Navigation

Search