Wildfire smoke resulted in the worst-possible air quality rating for Edmonton on Sunday. The Air Quality Health Index is a scale of one to 10+, or low risk to very high risk. Edmonton and surrounding counties were rated 10+ Sunday afternoon. Northern communities like Fort McKay and Fort Chipewyan were rated four, but expected to reach 10+ by the evening. As of Sunday afternoon, Environment and Climate Change Canada forecasted the conditions could last until Tuesday. According to the government agency, groups that are more vulnerable to the effects of wildfire smoke and should take precautions like limiting their exposure include people aged 65 and older, pregnant people, infants and young children, people with an existing illness or chronic health condition, and people who work outdoors. According to FireSmoke Canada, which is operated by the Weather Forecast Research Team at the University of British Columbia, the smoke is largely coming from wildfires in the Northwest Territories.