Sweden has a warning system called Important Public Announcement. The warning system includes outdoor signal horns or sirens. This system is popularly known as Hesa Fredrik (Hoarse Fredrik).
The sirens are tested four times a year, on the first Monday that is not a public holiday in March, June, September and December. The siren that sounds on Monday 7 March at 15:00 is therefore a test, not a real warning.
Bearing in mind the conflict in Ukraine, it may be a good idea to tell staff and students who are new to Sweden about these regular tests of the warning system.
Read more about Sweden’s warning system on the Swedish Civil Contingencies Agency website (in Swedish).