Haze blanketed Colorado on Monday as wildfire smoke drifted from Canada, and the gray skies are expected to hover overhead for at least another 24 hours.

The wildfire smoke led the Colorado Department of Public Health and Environment and the Regional Air Quality Council on Monday to issue public health advisories, recommending people limit outdoor activity. The smoke is increasing the amount of ozone and fine particulate matter in the air.

Air monitors across northern Colorado and the Front Range were showing high concentrations of particulate matter, which can be smoke, soot, ash or liquid particles that people can inhale.

The highest concentration as of 3:45 p.m. Monday was in Louisville, where air monitors recorded an air quality index of 537 PM2.5, nearly 16 times higher than the level of particulate matter considered safe by the Environmental Protection Agency, according to the agency’s fire and smoke map. People were advised to stay indoors.

The alert was issued for the Front Range, stretching from Douglas County to Larimer and Weld counties. It will remain in effect until at least 4 p.m. Tuesday.

The state health department also issued health advisories for Mesa, Moffat, Grand, Jackson and Routt counties. Poor air quality was forecast in Colorado Springs and Pueblo, as well.

People with heart or lung disease, older adults and children are especially vulnerable to wildfire smoke. They should avoid prolonged or heavy exertion while everyone else is advised to reduce outdoor activity.

The Regional Air Quality Council encouraged people to avoid driving and using gas-powered lawn equipment until after 5 p.m. when temperatures start cooling.

The Colorado Smoke Blog, which is run by the state health department, said the highest concentrations of smoke are at higher elevations in north-central Colorado, including the Park Range and northern parts of the Front Range. Rocky Mountain National Park also is covered by smoke.

Get more Colorado news by signing up for our Mile High Roundup email newsletter.

Originally Published: July 22, 2024 at 4:28 p.m.