Alert banners are posted on theweathernetwork.com by government agencies (I.e., Environment and Climate Change Canada), particularly when weather or other events are expected or occurring that could pose a threat to public safety, such as poor visibility, dangerous driving conditions and more.
In some cases, the alert is considered high priority and appears in full on the page immediately. This is to ensure that website users are aware of the event. Once a user has seen this page, a “cookie” is assigned to the user to represent that the page was viewed. Going forward, the regular forecast page will appear with the alert banner at the top, until the alert ends or is updated and re-issued.