First, the record Canadian wildfire season exposed residents of the biggest cities in the Northeast and mid-Atlantic to hazardous air quality. Now low-level smoke is taking aim at the Midwest and Ohio Valley.
Why it matters: Wildfire smoke is a public health hazard that can aggravate chronic conditions and pose risks for even healthy populations.
- Due to the wildfires' size, locations and behavior so far this summer, it's unlikely this will be the last time heavily populated areas of the country will see similar effects.
Zoom in: Chicago, Milwaukee and Detroit vied for the title of the city with the worst air quality in the world on Tuesday.
- In the Windy City, both O'Hare and Midway Airports saw visibility drop as low as 1.25 miles in smoke, as air quality index readings hit historic smoke-related readings.
Axios Local dispatch, via Justin Kaufmann in Chicago: When you walk out your door, the smell of smoke makes it feel like the fire is around the corner.
- Some Chicagoans have taken to wearing N95 masks for even the simplest tasks, like walking pets or commuting home. The haze is so strong that the Willis Tower is partially hidden from sight.
Between the lines: At the same time that Canada's fires were obscuring the Chicago skyline, people in Spain and Portugal (about 4,000 miles away) saw milky sunshine through a thick veil of smoke that made the trans-Atlantic crossing from Quebec's wildfires.
- Canada's wildfire season is now the worst on record since at least 1983, having burned 7.8 million hectares (19.3 million acres) through Tuesday.
- The fires are not expected to be extinguished, either by firefighters or a major shift in weather conditions, until after summer ends.
Context: Climate change is worsening wildfires and combining with other factors, such as land management practices, to yield larger blazes that exhibit extreme behavior.
- This is the case in the U.S. West and large parts of the affected areas in Canada, particularly given repeat heat waves in parts of Canada since May.
- Numerous instances of fire-generated thunderstorms have been observed in Canada so far this summer, a sign that the fires were burning at a high intensity.
- Wildfires burning in the boreal forests of northern Canada, which some of these blazes are doing, can have significant consequences for carbon dioxide emissions.
- The boreal forests ringing the Arctic store huge amounts of carbon, which is released when trees and soils burn.
The intrigue: The carbon dioxide emissions from Canada's wildfires through June 26 rank as the largest annual estimated emissions in the group's 21-year data set, according to the Copernicus Atmospheric Monitoring Service (CAMS) in Europe.
- Copernicus' scientists estimate wildfire emissions by using satellites to track the heat output from a fire, which is tied to the fire's consumption of fuels.
What's next: With fires burning upwind of the Midwest, northern Plains and Northeast, any weather pattern that features northerly winds aloft and near the surface could transport more smoke across the border in the months to come.
- In the near-term, air quality alerts are in effect Wednesday from Iowa and Minnesota to Washington, D.C.
