"Smoke is severely impacting air quality today", the Spokane Regional Clean Air Agency said in a tweet Sunday morning.
The poor air quality has also been affecting air travel in the province's interior.
"The millions of vehicles on Bay Area roads during these hot summer months create unhealthy air quality and make breathing more hard for many", said Jack Broadbent, executive officer of the air district.
Over the last week, all three Prairie provinces have been under special air quality statements for high smoke concentrations.
The National Weather Service has issued air quality alerts for much of Washington state.
The smoke is expected to move south on Monday and persist through the night.
"Local smoke levels may vary based on wind direction and fire characteristics but, until a significant change in the provincial weather pattern occurs, widespread air quality improvements are not expected".