When snow becomes dangerous: understanding heavy snowfall
Switzerland is no stranger to heavy snowfall. But when an unusually large amount of snow falls in a short time, it can cause serious problems across the country. The national risk analysis Disasters and Emergencies Switzerland (DES) 2025, published by the Federal Office for Civil Protection (FOCP), takes a close look at what such an event means for people, infrastructure and essential supplies.
What can happen?
When snow keeps falling, the country starts to grind to a halt. Rail lines and airports face disruption, and roads get shut down — not just in the mountains, but across the Swiss Plateau too (Figure 1). The weight of accumulated snow puts roofs, trees and infrastructure under serious stress. The results: collapses, roof avalanches, falling trees. Power lines and communications infrastructure are equally vulnerable — when they fail, outages can follow quickly.
https://blog.alertswiss.ch/assets/lbwp-cdn/alertswiss/files/1771921280/image1-1140x760.jpg Figure 1: Heavy snowfall in November 2024 paralyses daily life in large parts of Switzerland. [Source: Peter Klaunzer (Keystone)]
When the snow won’t stop – a possible scenario (DES 2025)
An already snowy winter takes a turn for the worse in mid-February, when a stationary front pushes large amounts of moist air in from the Atlantic. Over three days, the Swiss Plateau is buried under 50 to 70 cm of fresh snow — in some places up to 80 cm. Strong gusts drive additional drifting.
Clearance teams work around the clock, but the situation deteriorates faster than they can keep up. Secondary, roads become impassable and even motorways are reduced to a single lane. One by one, municipal, regional and cantonal emergency management teams are activated. Civil defence units are deployed and the army is called in to help. It isn’t enough — after about two days, traffic grinds to a complete standstill in many areas. Thousands of people are stranded in their vehicles and have to be evacuated over the following three days, with civil defence facilities, gymnasiums and other venues pressed into service as emergency shelters.
Meanwhile, falling trees and the sheer weight of snow bring down power lines and antennas, cutting electricity and telecommunications in affected areas. Difficult conditions on the ground and poor visibility in the air make repairs slow and helicopter rescue all but impossible.
Emergency call centres are overwhelmed by reports of accidents and missing persons, while rescue teams struggle to reach those in need. After two days, the effects begin to be felt in shops — supply chains are disrupted, shelves start to empty and panic buying makes things worse.
After three days, the snow stops and a high-pressure system moves in. Temperatures drop and stay below freezing. The immediate crisis eases, but recovery is slow: large stretches of the Swiss Plateau remain under 50 to 80 cm of snow, transport routes stay blocked and some buildings remain at risk of collapse.
The turning point comes quietly — clearance teams begin making rapid progress and most roads are reopened within two days of the snowfall ending, quickly easing the shortage of goods. Damaged power and telephone lines are provisionally repaired within three days and life, gradually, returns to normal.
Impact on the society, the environment and the economy (DES 2025)
Heavy snowfall leads to a significant increase in traffic accidents. Numerous people are injured or rescued from stranded vehicles, many suffering from hypothermia. The weight of accumulated snow can also cause roofs to collapse, putting lives at risk. Poor road conditions make emergency medical care considerably more difficult, while limited visibility often makes air rescue impossible.
The economic and infrastructure impacts are equally severe. Road, rail and air traffic are heavily disrupted, while damage to buildings, power outages and telecommunications failures affect businesses and supply chains alik[...]
