Wildfires burning in British Columbia are causing smoky conditions in Alberta and Saskatchewan.
Alberta Health Services has issued air-quality advisories in its north and Calgary zones.
It says even healthy people may feel irritation in their eyes and throat, as well as possible shortness of breath.
The health agency is advising people to minimize outdoor physical activity and keep windows and doors closed.
Environment Canada has also issued special air-quality statements for much of southwestern Saskatchewan.
It says children, seniors, and people with cardiovascular or lung diseases are especially at risk.