Health officials are warning people in Calgary and much of southern Alberta that smoke from forest fires to the west could linger in the air for several days — if not weeks.

The Air Quality Health Index for Calgary on Monday is forecast to reach seven out of 10 (high health risk) before dropping to four (moderate health risk) later in the day, and drop to three (low health risk) on Tuesday, according to Alberta Environment.

The smoke has also prompted both Alberta Health Services and Environment Canada to issue air quality advisories.

Some people even noticed ash on their vehicles Monday morning.

Against a dark surface, the ash falling in calgary from the Banff and BD forest fires looks like snow. Ash in cars over 20 minutes shown. <a href="https://t.co/zd4f1RZ6Hv">pic.twitter.com/zd4f1RZ6Hv</a> —@refmaksy

Those agencies are telling people to limit physical activity outside, stay indoors with the windows closed, and, if you're driving, run the fan on recirculate.

Officials say that at times the smoke may cause throat irritation, headaches or shortness of breath.

Children, seniors and those with breathing problems or heart conditions are especially at risk.

"At this important time, for people with those chronic health conditions, even with what we've got right now, it's better for them to be indoors," said Dr. David Strong, a medical health officer for the Calgary zone.

Wildfire near Sunshine forces park closures

One wildfire northwest of Sunshine Village, at Verdant Creek, has forced the closure of parts of Banff and Kootenay national parks.

Parks Canada says some popular hiking trails and backcountry reservations will be cancelled until at least Tuesday.

"The fire is moving to the northeast and is currently not threatening any local communities," said Banff field unit supervisor Dave McDonough on Monday.

"The fire is being actively managed by Parks Canada, using helicopters to bucket water to contain the fire."

He said smoke is making it difficult to determine the exact size of the fire, but a spokesperson later clarified it could now be as big as 2,000 hectares.

That's a significant increase from Sunday's estimate of between 150 and 200 hectares.

Improvements

Air Quality is expected to improve in Calgary, starting from the north, on Monday but levels may remain higher in areas closer to the Foothills.

A fire that broke out in a wooded area inside the city was largely put out by late morning, fire officials said. Someone had set up camp and left a stove unattended in a wooded area along Bow Trail where it meets Crowchild Trail.

Back in 2015, smoke from wildfires in B.C. and the northern U.S. lingered around Alberta for weeks — prompting multiple high risk alerts.