According to Alberta Environment and Parks, low temperatures in the winter months can influence air quality.
Air quality is measured by a network of monitoring stations called the Alberta Air Quality Health Index. It is then categorized into Low, Moderate, High or Very High Risk to health.
Pollution such as vehicle and industrial emissions usually are carried away by warm weather near the ground, but in colder weather cold air is trapped near the ground by a layer of warm air several hundred meters above it. The warm air acts like a lid, meaning pollutants can't rise and disperse as readily, leading to higher AQHI readings. Storms including snowfall and high winds rid the air of these pollutants.
Moderate to high AQHI readings may lead to health problems for "at risk" populations including children, the elderly and those with existing respiratory issues, according to Alberta Environment and Parks.
Current and forecast AQHI levels can be found at fortair.org.