How Canadian wildfire smoke impacts global air quality

The Northern Hemisphere is witnessing an alarming increase in the frequency and intensity of wildfires, and Canadian wildfires play a significant role in this global phenomenon. As flames engulf vast stretches of boreal forest, the smoke wildfires produce knows no borders; smoke travels thousands of miles, affecting air quality across North America and beyond.

Active wildfires in northern Canada on the morning of Wednesday, July 16. Source: IQAir.

And though Canada is home to vast, majestic forests and wildlands, transboundary wildfire smoke isn’t any one country’s problem – nor does it all come from one nation. It’s crucial to understand the interconnected nature of wildfire smoke in the Northern Hemisphere, as only a collective, coordinated effort will help manage and mitigate smoke’s well-documented health risks.

How wildfire smoke travels

When wildfires burn, they release a mixture of gases and fine particles into the atmosphere. These emissions don’t stay put; instead, they are carried by wind currents, sometimes traveling thousands of miles from the flames (1).

The key player in this journey is the jet stream, a high-speed air current that can swiftly carry smoke from Canadian wildfires down to the U.S. and even across the Atlantic to Europe. During the day, warm air rises, taking smoke high into the atmosphere where it catches a ride on these wind currents. At night, cooler air can trap smoke closer to the ground, leading to hazy skies and poor air quality.

Lingering wildfire smoke in the lower Great Lakes and along the St. Lawrence River on the morning of Wednesday, July 16. Source: IQAir.

The size and intensity of the fire also influences how smoke spreads, as explained by Dr. Christi Chester Schroeder, IQAir’s Manager of Air Quality Science.

“When wildfires burn with extreme intensity, the massive heat generates strong updrafts that can form pyrocumulonimbus (pyroCb) clouds,” she said.

“These towering fire-induced thunderstorms can inject smoke particles more than 5 miles into the upper troposphere, and in some cases, even into the stratosphere. Once suspended, these particles can be transported hundreds or thousands of miles and remain in the air for days to weeks, especially when it reaches the stratosphere.”

Breathing wildfire smoke carries health risks

When people breathe in smoke, they’re inhaling a mix of harmful gases and fine particles. These particles, known as PM2.5 – tiny particulate matter measuring 2.5 microns in diameter or less – are particularly dangerous because they can get deep into our lungs and enter our bloodstream, reaching every organ in the body.

Exposure to wildfire smoke can cause a range of health issues including (2):

• Burning eyes and runny noses
• Aggravated chronic heart and lung diseases
• Triggered asthma attacks
• Increased risk of heart attacks and strokes

Symptoms such as coughing, wheezing, and difficulty breathing can occur in children, the elderly, those with pre-existing health conditions, and – under more severe conditions, even healthy adults.

Global impact of Northern Hemisphere wildfires

Wildfire smoke doesn't respect borders. Smoke from Canadian wildfires has been known to drift south, blanketing major U.S. and Canadian cities in haze and significantly worsening air quality. In some cases, it has even crossed the Atlantic, affecting air quality in Europe.

It’s a phenomenon being experienced frequently over the past few years –

• March 2023: Canadian wildfire smoke affected air quality across the Rockies and into the Great Lakes.
• July 2023: Poor air quality from Canadian wildfires persisted over much of the U.S. Midwest and Great Lakes, triggering air quality alerts.
• August 2024: Smoke from western Canadian wildfires reached Europe (3).
• June 2025: Smoke from extensive wildfires in Canadian provinces drifted across the North Atlantic. Coupled with Saharan dust, air quality was poor in Central and Southern Europe, particularly in Italy and Switzerland.
• Mid-July 2025: Air quality in the Great Lakes region and nearly every Canadian province was poor as smoke drifted across the continent. 

Canada doesn’t stand alone as a source of transboundary smoke in the Northern Hemisphere. Neighboring Alaska has seen major wildfires and wildfire smoke affect the state and neighboring provinces in 2022, 2024, and 2025 (4). Wildfires in Russia burned 21.7 million acres by July, 2024 (5). And drying conditions through heat waves and other causes can lead to devastating summer wildfires anywhere in North America, Europe, and Asia, resulting in smoke that reddens skies far from their source.

Climate change fuels wildfires

Climate change is significantly altering the dynamics of wildfire seasons.

Rising global temperatures lead to longer, hotter, and drier summers, creating ideal conditions for wildfires to ignite and spread.

This shift isn’t just increasing the frequency of wildfires but also their intensity and the challenges associated with managing them. The annual average temperature in Canada has increased at roughly twice the global mean (average) rate (6).

Key factors influenced by climate change include:

• Increased heatwaves and droughts: These dry out vegetation, turning forests and grasslands into potential fuel for fires. In the Northern Hemisphere and in boreal forests, lightning strikes can easily spark vast, fast-moving fires across the landscape (7).
• Earlier snowpack melting: Snowpacks act as natural water reservoirs and are melting earlier due to warmer temperatures. This causes drier conditions during critical summer and fall months.
• Changes in weather patterns: Climate change contributes to stronger and more unpredictable winds, which can rapidly spread wildfires.

These elements can combine to create a more volatile and dangerous wildfire season.

How international cooperation can manage wildfire risk

Managing wildfires and mitigating their impacts requires global cooperation, as wildfires and their smoke transcend borders, affecting distant regions. International collaboration allows countries to share resources, knowledge, and strategies to better predict, prevent, and respond to wildfire events.

Efforts include joint research to improve prediction models and early warning systems, sharing best practices for prevention like controlled burns, and mutual aid agreements for coordinated response during large-scale events. These partnerships are vital for reducing wildfire impacts and protecting communities and ecosystems worldwide – and citizens can advocate for them.

Protect yourself from wildfire smoke

Here’s how to safeguard yourself from transboundary wildfire smoke.

• Download a free air quality app for up-to-date alerts and forecasts.
• Close all doors and windows. Set your HVAC system to recirculate mode.
• Use a high-efficiency air purifier to help filter out wildfire smoke.
• Contribute to your community’s outdoor air quality data.
• Stay indoors when possible; if you must go outside, wear a KN95/FFP2 mask.

The takeaway

The Northern Hemisphere’s increasingly intense and lingering wildfire seasons require international cooperation to effectively limit their widespread impacts. Transboundary wildfire smoke crosses oceans and borders, presenting a shared challenge that demands collective action to protect human health.

It’s essential to stay informed about air quality issues and tackle the root causes of increased wildfire activity. By advocating for smarter climate change mitigation policies and preparing for wildfire events, we can help create a healthier planet and safer communities for everyone.