Chicago First Alert Weather: Air quality falls to 'unhealthy' level in Chicago due to wildfire smoke

CHICAGO (CBS) -- Air quality in Chicago has fallen to the "unhealthy" category, due to smoke associated with wildfires burning in Canada – moving in behind a cold front.

The air quality dropped from moderate to unhealthy Friday afternoon.

Air quality will improve from north to south after sunset, and is expected to be in the "good" category for Saturday.

AirNow warns that people with heart or lung disease, older adults, children and teens, should take precautions to avoid exposure. Those precautions include avoiding strenuous outdoor activities and keeping all outdoor activities short, and either moving physical activities indoors or rescheduling them.

Everyone else should choose less strenuous activities – such as walking rather than running – to avoid hard breathing. Everyone should also shorten time outdoors, and wait until air quality is better to be active outside.

CBS 2's Kris Habermehl reported slightly blurred visibility in Chopper 2 as the smoke mixed into the lower atmosphere.

The wildfires are burning particularly in the province of Alberta, where tens of thousands of people have been evacuated.

In:
• Wildfire
• Wildfire Smoke