CANADA - Canadian wildfires continue to affect the country as more than 500 active wildfires rage across Canada. As CNN reports, some fires are so out of control, officials have no choice but to leave them burning. Recent updates show another wave of ground-level smoke has returned to the United States, dropping air quality levels across much of the northern part of the country.

At least 10 countries have deployed their own firefighters to assist Canada with putting out the ones threatening communities whose residents have scrambled to evacuate, reported CNN. Massive fires are burning in remote areas, such as northwestern Quebec, making it too dangerous for local firefighters to tackle.

“If you have limited resources, and you have a lot of fires, what you do is you protect human life and property first,” Robert Gray, a Canadian Wildland Fire Ecologist, told CNN. “You protect people, infrastructure, watersheds, so there’s a prioritization system.”

NPR reported smoke will be affecting much of the Midwest and East Coast of the United States, noting it’s the worst Canadian wildfire season on record thanks to unusually high temperatures and dry conditions. NASA satellites have recorded some smoke trails traversing the Atlantic too, as far afield as Spain and Portugal.

The smoke is forecast to shift out of the Canadian Rockies and Prairies into the neighboring northern Plains and Northwest U.S. into Wednesday, leading to poor air quality and low visibility, AccuWeather forecasters warn.

ANUK will keep an eye on the wires for more updates.