Here’s where wildfire smoke is spreading in Canada and the U.S.

As wildfires continue to rage in Western Canada, communities in affected areas and surrounding provinces have been blanketed by thick plumes of smoke, prompting air quality alerts extending into parts of the United States this week.

Smoke conditions in some parts of the U.S. Midwest have become so bad that the air quality has been categorized as “hazardous.”

Exposure to wildfire smoke has been found to cause early death and respiratory issues, says a 2024 report from Health Canada.

Which provinces have been affected so far?

Air quality warnings have been issued by Environment and Climate Change Canada throughout Manitoba, Saskatchewan, Alberta and Ontario. Fifty-three communities in southeastern Manitoba, for example, have received alerts about wildfire smoke causing poor air quality and reduced visibility.

The warnings stated that conditions in some Manitoba regions are improving as the smoke drifts eastward and away from the affected communities, but it is expected to linger in areas like Flin Flon and Cross Lake, where local wildfires are still evading control. 

Communities in northern Saskatchewan, such as La Ronge, have also been under air quality warnings for the past several days. While La Ronge is still on standby for evacuation orders, the Lac La Ronge Indian Band opened a fresh air shelter inside the Jonas Roberts Memorial Community Centre to provide some relief for those impacted by the heavy smoke.

A number of special air quality statements were also issued for more than a dozen communities in northwestern Ontario early Monday morning. The statements warned that wildfire smoke was expected to remain in the area for the next several days.  

What parts of the U.S. will be impacted? 

Over the weekend, smoke drifted toward the Upper Midwest in the U.S., impacting northwestern Wisconsin, eastern Nebraska, northeastern North Dakota and most of Minnesota.

A statewide air quality alert has been issued for Minnesota until Wednesday by the Minnesota Pollution Control Agency. The alert states that the smoke will likely reach northwest and north-central Minnesota by Monday evening, following behind a cold front that’s moving southeast.

The Air Quality Index values used in the U.S. are expected to reach the “hazardous” category in northwestern Minnesota. At that level, the public is advised to avoid physical activity outdoors, and high-risk groups — including those with lung and heart disease, seniors and young children — should remain indoors.

The alert warns residents in northwestern Minnesota that they can also expect mild ashfall and reduced visibility. 

Where is the smoke headed?

The smoke is expected to drift southeast in the coming days, according to BlueSky Canada’s smoke forecast, which combines Alberta and British Columbia’s forest fire data with weather forecast models to predict smoke concentrations. 

How bad is the air quality? 

Air Quality Health Index (AQHI) values — the scale used in Canada to relate air quality to health — were at seven in Flin Flon on Monday evening, putting it in the “moderate” health risk category.

An air quality warning for Flin Flon issued on Monday morning stated: “During heavy smoke conditions, everyone’s health is at risk regardless of their age or health status.”

The scale comprises four categories, ranging from “low” health risk to “very high.” The AQHI values are grouped into these categories, with any value from one to three deemed a low health risk to the general public and a value of 10 or more posing a very high risk.

In Winnipeg, the AQHI was at four, posing a “moderate” health risk. In Saskatchewan, most regions were observed to have AQHI values at “low risk” on Monday evening.

Fort McMurray and Grande Prairie in Alberta were at seven and eight, respectively, putting them in the “high risk” category.

Air quality can vary from hour to hour, and smoke conditions can change over short distances, an air quality statement for Grand Rapids and Easterville in Manitoba stated. 

Who will be most affected? 

According to Environment and Climate Change Canada, the people who are at the highest risk of facing health impacts due to low air quality caused by wildfire smoke include: 

• Seniors.
• Young children.
• Pregnant women.
• People who work outdoors.
• People involved in strenuous outdoor activities.
• People with chronic health conditions, such as:
  • Cancer.
  • Diabetes.
  • Lung or heart conditions, including asthma.
  • Mental illness.

When AQHI values are at “moderate” to “very high risk” levels, those who are at higher risk are advised to reduce or completely avoid strenuous outdoor activities entirely. 

What are long-term effects of wildfire smoke exposure?

In a fact sheet about the health effects of wildfire smoke, the B.C. Centre for Disease Control stated that smoky air can increase the risk of ear infections in children and pneumonia COVID-19.

The centre lists portable air cleaners with HEPA filters as a way to remove smoke particles from indoor air. It also recommends keeping car windows closed when driving and air conditioners turned on to limit letting in outside air as much as possible.

According to a 2024 report by Health Canada’s Water and Air Quality Bureau, there was “strong and consistent evidence” that wildfire smoke exposure can cause “premature mortality” and respiratory issues.

The report also concluded that exposure to wildfire smoke can worsen pre-existing asthma and chronic obstructive pulmonary disease.