Parts of Saskatchewan, including Saskatoon, remain under an air quality advisory.
Environment Canada says smoke from wildfires north of Hudson Bay is pushing into central regions of the province.
The smoke is producing extremely poor air quality, the agency said.
Shifting winds are expected to start pushing the smoke northward overnight and into Wednesday.
The advisory includes Prince Albert, the Battlefords, Hudson Bay, Melfort, Humboldt, Yorkton.
As of Tuesday morning, 13 wildfires were burning in Saskatchewan. Eight of those are north of Hudson Bay, with five currently not contained.
The Saskatchewan Public Safety Agency said it is responding to the wildfires with helicopters and ground crews.
The SPSA said a fire ban is also in place for most of east-central Saskatchewan due to hot and dry conditions and increasing fire activity.
Environment Canada said individuals may experience symptoms such as increased coughing, throat irritation, headaches or shortness of breath due to poor air quality.
Those most at risk are children, seniors and people with cardiovascular or lung disease, such as asthma or COPD.
Officials said outdoor activity and any strenuous physical activities should be limited as much as possible.
They also recommend keeping all windows and doors closed and setting HVAC systems to recirculate.
More information and advice on health risks, symptoms and precautions are available by contacting HealthLine 811.
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