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Hazard category 5 (very severe hazard)
Possible impacts
  • The level of bodies of water may rise rapidly
  • Sudden landslides are possible on steep slopes
  • Localised flooding may occur, particularly in underpasses, underground garages and cellars/basements
  • In mountainous areas, sudden debris flows may occur along stream courses
  • Traffic/transport routes may be restricted – longer journey times and an increased risk of accidents are to be expected
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
  • The level of bodies of water may rise rapidly
  • Sudden landslides are possible on steep slopes
  • Localised flooding may occur, particularly in underpasses, underground garages and cellars/basements
  • In mountainous areas, sudden debris flows may occur along stream courses
  • Traffic/transport routes may be restricted – longer journey times and an increased risk of accidents are to be expected
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
  • The level of bodies of water may rise rapidly
  • Sudden landslides are possible on steep slopes
  • Localised flooding may occur, particularly in underpasses, underground garages and cellars/basements
  • In mountainous areas, sudden debris flows may occur along stream courses
  • Traffic/transport routes may be restricted – longer journey times and an increased risk of accidents are to be expected
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 impactsThe level of bodies of water may rise rapidly where the ground is already saturated
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)

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