Alarms & sirens in Switzerland

Switzerland has a nationwide siren network that is designed to alert the public in the event of danger such as fire, flood, disaster or another emergency. It’s a good idea to learn what these alarms and sirens in Switzerland sound like and what they mean, so you know what to do if you hear one. 

Polyalert: A network of alarms all over Switzerland

The Swiss government developed the Polyalert system to ensure that it could quickly and comprehensively warn the Swiss population in emergency situations, and ensure that the same information is shared through each channel. 

The Polyalert system comprises of three key channels: 

• Sirens: There are 5.000 fixed and 2.200 mobile sirens in Switzerland. 
• The Alertswiss app and website: The Alertswiss website and accompanying app provide live updates, alerts, warnings and information based on the user’s location.
• Radio announcements: If necessary, alerts and warnings are also read aloud in German, French, Italian and English on the radio. This is a good backup, for instance, in case the internet fails. 

Types of alarms

There are two types of alarm in Switzerland:

• The “general alarm”: lasts for one minute and is repeated at two-minute intervals
• The “flood alarm”: lasts for 20 seconds and repeats every 10 seconds 

You can hear what the two different alarms sound like on the Federal Office for Civil Protection website.

What to do when the general alarm is sounded

The general alarm is used when there is a potential danger to the population, such as a natural disaster or war. If you hear the general alarm, it means that an official announcement or instructions will soon follow. 

You should:

• Listen to the radio or check the Alertswiss website or app
• Follow the instructions
• Inform your neighbours, in case they are not aware 

What to do in case of a flood alarm

The flood alarm is only used in areas downstream of dams and is sounded should risk of flooding ever occur. 

If you hear a flood alarm, you should:

• Leave the danger zone immediately
• Wait for further instructions and follow them

Testing the alarms in Switzerland

All alarms in Switzerland are tested annually, on the first Wednesday of February. In 2026, they will be tested on February 4. Residents are notified beforehand and no further action needs to be taken. 

Testing takes place at the following times:

• Between 1.30pm and 2pm: The general alarm is tested nationwide. 
• Between 2pm and 4.30pm: The flood alarm is tested in areas close to dams. 

If you hear either general alarm or flood siren outside of these scheduled testing times, it means that there is potential danger. You should check the Alertswiss app or listen to the radio. If you hear the flood siren and it is not a test, you should leave the area immediately. 

Alarms on Swiss lakes

To protect the safety of swimmers and boat users, every Swiss lake has a designated alarm system to warn lake users of an impending danger. These systems are usually flashing amber lights that have to be visible on all areas of the lake. 

The alarms have different meanings:

• A slow rotation of an amber light is used to signify a small danger such as a strong wind, rough conditions or hazards in the water.
• A continual flashing amber light indicates a danger related to weather, hazards or flooding. If you are on the water when this light is flashing, you should get out of the water.

Iodine requirement in Swiss houses

Switzerland currently uses three nuclear power plants to produce electricity. If you live within 50 kilometres of one of these nuclear power plants (which includes major Swiss cities like Zurich, Basel and Aarau), your local council (Gemeinde) will provide every resident with a dose of Iodine to be taken in the event of a nuclear meltdown, signalled by a general alarm and subsequent radio alert. 

Do not take this medication until instructed to do so by an official source.