On Saturday July 20, Environment Canada issued an alert at 18:15 and 18:30. 
These alerts on broadcast over-the-air stations air at different times on each station.
I didn't see any alerts run on CBLT nor CFTO during their newscasts; I don't know if they mentioned them.
CITY-TV was first to air the alerts at 18:17 (during a commercial) and 18:32.  There was no audio, just a middle of the screen large scroll, white on red with buzzards.
Global was second a few minutes later but with a full screen white on red alert with audio, over their newscast which looked awkward.
TV Ontario was next with text and audio in English and French.