On the first Wednesday of each month at 12:00 hours, the City of Prague Fire Services and Operations Center operates and maintains the warning system by activating the alarm- siren.
Mermaids are often followed by a message (in Czech and English) about the nature of the emergency or confirming that it is only a test. The alarm is a deep and disconcerting sound that sounds for 140 continuous seconds through the system of hundreds of speakers scattered throughout the city.
The warning system originated in World War II when the Czech Republic was still Czechoslovakia. The sirens were not exclusive to Prague but were activated throughout the country. Mermaids aim to protect citizens by ensuring they are notified of imminent or incurred danger. At this time and during the Cold War, they were intended to warn citizens of activities that could endanger the lives of the locals, such as an earthquake or other life-threatening incident, for example in 2002, large floods caused the use of the sirens to evacuate more than 40,000 people from the city center.
Do not be scared to hear the sound of the siren, it is one of the services that guarantee the safety and care of the inhabitants of the city. Pay attention and trust the information.