Don't be alarmed if you get a emergency alert on your phone today.
The Canadian Radio-Television and Telecommunications Commission will be testing the system in all provinces and territories except Nunavut today.
The exact time of the test varies by location, but residents do not need to take any action when their phones go off.
Ontario's test is expected just before 1 p.m.
In the past the tests have received criticism - many phones failed to light up when the first test of the system was conducted in Ontario in 2018.
Subsequent tests have been more successful.