Thick plumes of smoke from blazes in the Canadian province of Alberta crossed into multiple states including Montana, Colorado, Idaho and Utah.
But a Pacific cold front moving into the area toward the end of the weekend was expected to bring rain and wind that could push the smoke away.
Officials in Montana said Sunday that nearly the entire state was being impacted by the wildfire smoke and issued an air quality alert for more than three dozen counties. Some areas were experiencing “very unhealthy” air quality levels.
The National Weather Service station in Glasgow, Mont., also deemed the air quality “very unhealthy” and urged people to limit their time outside, close their windows and refrain from burning any debris.
Swaths of eastern Colorado were also affected, with the metro areas of Denver and Colorado Springs seeing unhealthy air quality levels at points on Sunday.
An air quality health advisory for wildfire smoke was in effect until at least 4 p.m. local time.
“If smoke is thick or becomes thick in your neighborhood you may want to remain indoors,” the advisory warned. “This is especially true for those with heart disease, respiratory illnesses, the very young, and the elderly.”
Conditions were expected to improve but some health impacts to residents, particularly those at higher risk, were still possible through Sunday afternoon, Colorado officials added.
Utah and Idaho also began to see smoke from the wildfires on Friday and warned vulnerable residents to be careful.
Canadian fire officials issued issued a special air quality statement for much of Alberta and said wildfires this year alone have burned more than two million acres, according to the CBC.