Why Wildfire Smoke Is So Dangerous

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Last week was the second major invasion of smoke into the Midwest and Northeast U.S. from a rash of Canadian wildfires. It set particulate pollution records in Chicago, Detroit and Pittsburgh, among other cities.

Now computer forecast models are suggesting a U-shaped “trough” of low pressure will set up next week somewhere in eastern Canada. While that will drive cooler, less humid air into the northern U.S., it also could bring some Canadian wildfire smoke.

(​MORE: Here's What Wildfire Smoke Does To Your Body)

But this scenario is more complicated and may have key differences compared to the June smoke events. First off, this trough may set up farther west and north over Ontario or Hudson Bay, rather than over the Great Lakes or Northeast U.S. as it did in June. That would keep it from pulling smoke southward from the particularly large cluster of fires in Quebec.

Next week’s pattern could also bring badly needed soaking rain to the Ontario and Quebec wildfires. However, some of that rain, especially in Quebec, could be in the form of scattered thunderstorms. These storms could produce lightning strikes capable of starting new fires or producing shifting winds, making it harder to keep fires away from populated areas.

This U-shaped trough could also pull in at least lofted smoke from the larger fires in Saskatchewan, Alberta and British Columbia into parts of the northern U.S. How much of that smoke makes it to the ground next week is a bit uncertain, but those nearest to the Canadian border from Montana to the northern Great Lakes could experience at least some smoke, at times.

C​omputer guidance continues to suggest that at least some smoke will make it over the border in those areas by Monday as a cold front sinks into the U.S. Some of this smoke could be pushed southward across the Midwest on Tuesday.

After the first smoke episode in early June, we explained why cold fronts the rest of summer could pull wildfire smoke into the U.S., as long as those Canadian fires continue. So this is a reminder that we’re likely not finished with wildfire smoke. On The Weather Channel app, you can monitor your daily air quality and also turn on “government-issued alerts” to receive any air quality advisories that may be issued in your area.

Y​ou can track the real-time air quality for your area at this link.

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