The familiar sight of Pikes Peak was hidden behind a hazy curtain Monday as smoke continued to drift across Colorado from several large wildfires burning in areas outside the state, including Canada.

The U.S. Air Quality Index measures air breathability on a scale of 0 to 500, with readings between 0 and 50 indicating “good” air quality. According to IQAir.com, the Front Range and much of the state is currently in the “moderate” category (between 51 and 100 AQI). On Monday, Colorado Springs’ air quality index was 62.

The Colorado Department of Public Health and Environment advised Front Range residents to exercise caution while outside over the next few days, including moving outside activities indoors or rescheduling until the haze clears.

Children, older adults and people with heart or lung problems were advised to avoid “prolonged or heavy exertion” on Monday and Tuesday, the state health agency said. Anyone who is sensitive to smoke or other air pollutants should consider wearing a mask outdoors and keep their windows closed.

According to the National Weather Service in Pueblo, the smoke was expected to continue flowing in from the Pacific Northwest and Canada on Tuesday and Wednesday.

“By late this week — probably Thursday, going into Friday — we’ll get more of a southwesterly (wind) flow aloft, and that should help take the smoke eastward,” said Weather Service meteorologist Kathy Torgerson.

“But there are some fires in southwestern California too. We should see improved conditions late in the week, and we’ll see what happens after that.”