At least 30 new fires broke out across the country’s expansive forests on Tuesday, according to a Wednesday situation report from the Canadian Interagency Forest Fire Center (CIFFC). 
 

That brings the total to nearly 500 active fires burning across Canada — more than 250 of them currently listed as out of control.  
 

Canada is in the midst of its worst fire season on record — plagued by blazes that have already consumed an unprecedented 29,000 square miles, an area nearly the size of South Carolina.  
 

To put those numbers in a different context, nearly 14 times as much Canadian land has burned up so far in 2023 as would burn in an entire average 21st-century year, according to CIFFC. 

The rash of uncontrolled fires is sending smoke billowing south and across some of the Midwest’s biggest cities, leaving them with some of the unhealthiest air in the world.  

As of press time on Wednesday, only the scorching, petroleum-choked metropolis of Dubai had worse air quality than Detroit, Chicago and Minneapolis.  

For Canada, the fires are a national phenomenon, burning in every province and territory except for rainy, wind-swept Prince Edward Island, according to CIFFC.  

About 46 percent of the nearly 3,000 fires burning throughout Canada are spread across the heavily forested western provinces of British Columbia, Alberta and Saskatchewan. 

Another 16 percent (500 fires in total) are burning in the eastern province of Quebec — consuming more than a third of the total land that Canada has lost to fire this year. 

And these eastern blazes have had a wide range of consequences, such as disruptions to the region’s thriving gold mining industry, S&P Global reported. 

The air blowing south from Canada is unhealthy largely because of what it carries: masses of tiny, floating soot particles left over from the large-scale combustion happening in the nation’s forests. 

The biggest public health threat from the fires comes from fine particulate matter, or PM 2.5 — particles so small that they can cross into the bloodstream. The biggest PM 2.5 particles — which must have a diameter less than 2.5 microns — are about 30 times smaller than a human hair.  

Each of the three top contaminated Midwestern cities had PM 2.5 levels that were at least 15 times greater than concentrations deemed safe by the World Health Organization (WHO), according to data from IQAir.  

Smoke from the fires has even crossed the Atlantic, where it has helped push Madrid to PM 2.5 levels more than four times greater than the WHO threshold. 

Stuck in smoky conditions? Building indoor air cleaners can help protect lungs and hearts, according to the California Air Resources Board, which has spent nearly a decade trying to keep people safe amid worsening smoke events. 

For those in need of faster and less expensive relief, the Environmental Protection Agency has a guide for how to create a simple-but-reliable DIY ‘clean room’. 

The Confederated Tribes of the Colville Reservation, meanwhile, offers a video tutorial on how to build a freestanding, two- filter homemade air purifier using air filters and a couple box fans.  

You can keep up with the air quality news on TheHill.com.

Welcome to The Hill’s Sustainability newsletter, we’re Saul Elbein and Sharon Udasin — every week we follow the latest moves in the growing battle over sustainability in the U.S. and around the world.

Surging global temperatures are shifting would-be snowfall to rain — making mountain communities across the Northern Hemisphere more vulnerable to devastating landslides, floods and soil erosion, a new study has found.  

Rain replacing snow: Warmer weather — fueled by climate change — has long been expected to increase the volume of precipitation falling during extreme events, the study authors acknowledged. 

But the fraction of water falling as snow in mountainous regions has plunged, in favor of rain — which has the potential to trigger floods and other calamitous events, according to the study, published on Wednesday in Nature. 

A direct effect: “One quarter of the global population lives in or downstream from mountainous regions,” first author Mohammed Ombadi, of the Department of Energy’s Lawrence Berkeley National Laboratory, said in a statement.  

They are going to be directly affected by this risk,” Ombadi added.  

Quantifiable change: The Berkeley Laboratory scientists were able to quantify the shift in the results of their research.  

• For every degree-Celsius rise in global temperature, they calculated an average of 15 percent more rain at higher elevations.  

Which mountains are at greatest risk? While all of the mountain ranges in the Northern Hemisphere are incurring shifts from snow to rain, some are facing bigger threats than others, the researchers found.  

• Among the most vulnerable are the mountains of the North American Pacific, such as the Cascades, the Sierra Nevada and coastal ranges from Canada to Southern California. 
  
  
• Also at risk are the Himalayas and other high-latitude regions.  

Why these particular ranges? The scientists said that they are still working to understand why certain regions are under greater risk than others. 

• North American Pacific ranges may be more susceptible because a significant share of snowfall there “occurs at temperatures just below zero degrees Celsius,” Ombadi explained. 
  
  
• “The slightest change in air temperature will shift this snowfall to rainfall,” he added. 
  

What can be done? Ombadi expressed hopes that fellow scientists will use this distinction between snowfall and rainfall to help improve global climate models.  

• Civil engineers, meanwhile, could harness the data to prepare for extreme weather events, according to Ombadi.  
  
  
• Such information could contribute to the design of infrastructure capable of withstanding the negative effects of extreme weather, he added. 

A single degree means a lot: As countries strive to limit global warming to 2 degrees Celsius above preindustrial levels, Ombadi urged them to consider “the linear relationship” between warming and rainfall.  

• “For instance, 1 degree [Celsius] of warming causes 15 percent more rain, while 3 degrees leads to a 45 percent increase in rainfall,” he said.  
  
  
• Ombadi emphasized the need to invest in technologies that could help reduce emissions, while also “preparing for the consequences of warming now.”