Wildfire smoke in Niagara region, St. Catharines, ON, 15 July 2026 (photo from Wikimedia)

19 July 2026

As I wrote on Friday 17 July, wildfire smoke has been plaguing the northeastern U.S. and the Great Lakes region in the U.S. and Canada.

The photo at top shows the worst day in the Niagara Falls area as seen in St. Catharines on Wednesday 15 July. Pittsburgh’s worst day was Friday the 17th, shown in the video below.

The source is nearly 1,000 forest fires in northern Minnesota and western Ontario, most of them at least a 1,000 miles away. Across the continent there are many, many more. Here’s what’s burning in North America this morning according to NASA’s Fire Information for Resource Management System US/CANADA map.

Wildfires in North America on 19 July 2026 (NASA FIRMS US/CANADA)

On Friday Pittsburgh’s air was so bad it was Hazardous (Maroon color) …

… shown on the PurpleAir map(*), Friday 17 July 2026 at 6:42am EDT. I’ve made it tiny so you won’t confuse it with today’s map. Click on the image for a larger view.

Happily the air cleared Saturday at noon and air quality improved into the Orange zone (considered a high rating but alas fairly common Pittsburgh’s Mon Valley). I went out for a walk and, though it was nice to be outdoors, it was so humid I dripped with sweat.

Today’s air quality should be even better, right? Nooooo! It’s in the Red Zone.

PurpleAir map North America as of 19 July 2026, 6:54am

Why is it worse? Why is it here at all?

This wildfire smoke comes to us on upper level winds that pass over the fire area before they reach us. (Wildfire smoke has risen that high!) Notice how the jet stream is coming from the fire zone this morning at 7:18am. Pittsburgh is the black dot.

screenshot, 250hPa. From earth:: a global map of wind, weather and water, 19 July 2026, 7:18am EDT

On Saturday upper level winds were coming from the Great Plains so our air was better. (I’ve added a wobbly green arrow to Saturday’s map to point this out. Pittsburgh is the black dot.)

screenshot, 500hPa. From earth:: a global map of wind, weather and water, 18 July 2026, 9am EDT

So I’m hoping the jet stream will wobble and give us good air. Then we’ll breathe easy.

And… a Huge Debt of Gratitude to Hudson Valley Weather on Facebook for their excellent description of the origin and persistence of the fires and upper-level transport. Their Facebook post is well worth a read.

p.s. (*) PurpleAir’s interactive map has a dot for each air quality monitor providing realtime data to their network. Some of the dots are government AQ monitors but most are individuals and organizations like GASP that want/need to know the air quality in their area.