Forecasters with the National Oceanic and Atmospheric Administration say the smoke and the oppressive heat that have plagued different parts of the U.S. will continue to be a problem for some time.
The weather pattern contributing to both fires and heat waves shows no sign of letting up for a week or longer, according to meteorologists.
They say the jet stream is , leading to conditions that keep weather stalled in place for long stretches.
A heat dome has spread north and east from Texas into the Midwest and as far east as Florida, and could see unusually high temperatures going into the next week.
Meanwhile, the particularly hot and dry conditions have supercharged fires in Canada, which is now dealing with its worst wildfire season in modern history. More than have burned, and are still out of control.
Smoke from the fires has covered American cities in smog, canceled events and prompted air quality alerts for more than 120 million people across the U.S.
Experts say as long as the weather stays stalled as it is, those problems will continue.
“While the fires are ongoing, you can expect to see these periodic bad air days and the only relief is either when the fires go out or when the weather pattern dies,” University of Chicago atmospheric scientist Liz Moyer told The Associated Press.
Local low-pressure systems can provide some relief as they move through, but in some cases their winds draw more smoke down from the north, or more hot air up from the south. For example, forecasters say a place like St. Louis could expect better air quality in the next week — but it might have to deal with triple-digit temperatures and high humidity instead.