Alberta Health Services has issued an air quality advisory for Edmonton and surrounding communities.
In a written release, AHS said smog, caused by a buildup of pollutants during light wind conditions and changing temperatures, is leading to poor air quality.
AHS said the smog could cause health problems, particularly for people with respiratory problems.
"The quality of air at present is not a health hazard for those in good health," said senior medical health officer Dr. Gerry Predy.
"However, people with asthma, bronchitis or emphysema should monitor their reactions and take any preventative measures their physicians have previously recommended."
Predy also advised people with respiratory conditions to remain indoors, keep their windows closed and limit outdoor physical activity.
The warning is expected to last through the weekend.