A wildfire burns in northern Manitoba, Canada, on 14 May 2024
Canadian Press/Shutterstock
The North American wildfire season is off to an active start: in May, large wildfires in western Canada prompted evacuations and sent smoke drifting through the atmosphere over the US Midwest, temporarily giving the region the country’s worst air quality. This past week, smoke from wildfires in Mexico was blowing north, worsening air pollution in the US Southeast.
Here is what we could expect for the wildfire season ahead.
Will this year’s wildfire season be as bad as 2023?
We have good reason to think the fires will be milder than last year’s, and the skies may not get quite as smoky. But forecasts suggest we could still see a particularly active wildfire season.
In 2023, most North American wildfire activity occurred in Canada, where around 18 million hectares burned – more than double the record set in the 1990s. Unusually persistent hot and dry “fire weather” throughout the season drove these blazes.
“Last year was a record-smashing, exceptional year,” says Mike Flannigan at Thompson Rivers University in Canada.
It is statistically unlikely that the same extreme conditions will repeat this year, says Flannigan. And the shift to La Niña conditions in the Pacific Ocean could in fact bring wetter weather to much of Canada.
Even if this year’s fire season is tamer than last year’s, the US National Interagency Fire Center says ongoing drought and above average-temperatures could trigger higher than normal wildfire activity in much of western Canada and parts of the US – the latter, as a whole, saw relatively low wildfire activity last year.
“We have to wait and see,” says Flannigan.
What is happening with the wildfires right now?
Mexico’s wildfire season is nearing an end with a burst of above-average activity. On 21 May, the country’s national forest agency reported 121 active fires covering 93,000 hectares, mostly in the west and south. Fire smoke has brought unhealthy air quality to parts of Mexico, as well as Texas and areas of the south-east US.
Canada’s wildfire season began in early May with large fires in the west – especially in British Columbia, where thousands of people have been evacuated this month. Emissions from the fires in the first two weeks of May set a record for the province, according to the European Union’s Copernicus weather service. The country’s overall wildfire emissions remain relatively high, but still much lower than this time last year.
“We’re off to a quick start,” says Flannigan. But he cautions against interpreting this as a sign of what is to come. The spike in early season activity could have resulted in part from last year’s fires in Canada spurred by drought. Since last year’s blazes, hundreds of “zombie fires” have continued to smoulder. Wetter, cooler weather could reduce the fires later in the season, he says.
Smoke billowing from several fires around Fort Nelson, Canada, and streaming east into Alberta on 11 May 2024
ZUMA Press, Inc. / Alamy
How many people will be affected by wildfire smoke?
Last year, wildfire smoke blew south from Canada over large parts of the US, producing dramatic orange skies and thick smog in cities like New York and Washington DC, worsening air quality for millions of people.
If a smaller area burns this year, Flannigan says, the US could expect less smoke. But the many factors involved make predicting wildfire smoke very tricky. Forecasters must consider exactly where fires will burn, how high the smoke will be injected into the atmosphere and where it will travel. “It gets really messy really quick,” he says.
What are the health risks of exposure to wildfire smoke?
Worsening wildfires linked to human-caused climate change have slowed or reversed years of progress in reducing US air pollution. According to one recent study, the additional mortality due to exposure to wildfire smoke could represent the deadliest and costliest consequence of climate change in the US.
Wildfire smoke has a different composition than typical urban smog, says Peter Thorne at the University of Iowa. It contains the same type of pollution, small particles known as PM2.5, but can also include other harmful and potentially carcinogenic pollutants depending on what is burned. These might include organic material like wood from blazes in forests, or synthetic material like asbestos when buildings burn.
Even a few days of exposure to high levels of wildfire smoke can exacerbate respiratory conditions like asthma or chronic obstructive pulmonary disease (COPD), says Thorne. As with other types of small particle PM2.5 pollution, chronic exposure may also impair the immune system and increase risk for heart attacks, among other conditions.
If North America faces another smoky season, you can take steps to reduce your exposure to wildfire smoke. For instance, on days with bad air quality, stay indoors and use air filters. And if you must venture outdoors, wear a high-quality mask.
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