An emergency population warning is a method where by local, regional, or national authorities can contact members of the public to warn them of an impending emergency. These warnings may be necessary for a number of reasons, including:Weather emergencies such as tornadoes, hurricanes, and ice storms. Geological disasters such as earthquakes, landslides, volcanic eruptions, and tsunamis. Industrial disasters such as the release of toxic gas or contamination of river water. Radiological disasters such as a nuclear plant disaster. Medical emergencies such as an outbreak of a fast-moving infectious disease. Warfare or acts of terrorism.

The National Public Alerting System, branded as Alert Ready, is the national warning system in Canada, broadcast to Canadian television, radio, and wireless devices.