Canadian Wildfire smoke

It’s smoke from the Canadian wildfires.

Canada wildfires choke skies across 5 states, creating unhealthy air quality for millions

The majority of them are not under control, and some of them are too remote to even try to fight. They’ll burn until winter. And some of them may start up again in the spring, even under feet of snow the stumps and roots can continue to burn and will crawl out again when the snow melts.