Environment and Climate Change Canada (ECCC) has issued a special air quality statement for Calgary, saying that "stagnant winter weather conditions" have created elevated pollution levels in the city.
The warning was issued shortly after 4:30 a.m. MT on Sunday. The air quality is expected to improve over the course of the coming week.
Justin Patten, a meteorologist with ECCC, said an extremely stable air mass has been parked over the city for the past few days, trapping air — and pollution — close to the ground.
"What we've seen the last couple of days is a slow increase in the air quality values to the point now where they hit the conditions where we issue the special air quality statement," Patten said.
He said these conditions will persist until stronger winds and warmer temperatures disperse the stable air from the area.
"It's looking kind of like early to mid-week right now. There are westerly winds in the area; whether or not they'll get into Calgary is something that we're going to watch over the next day or two," he said.
"We'll be looking for that kind of windy, a little bit gusty, conditions to start mixing some of the pollutants away from the surface."
In the meantime, Environment Canada says people may experience symptoms such as increased coughing, throat irritation, headaches or shortness of breath. Children, seniors, and those with cardiovascular or lung disease, such as asthma, are especially at risk.
"If you are experiencing symptoms, such as coughing or throat irritation, consider reducing or rescheduling strenuous outdoor activities until the special air quality statement is lifted," the statement said.
Residents are also asked to reduce air pollution by limiting the amount of wood burned outdoors in fire pits and by burning only dry seasoned wood.