Smoke coming in from Canadian wildfires settled over Chicago, causing unhealthy air quality conditions for at-risk groups. The Environmental Protection Agency is set to send out another air quality alert for Saturday.

An air quality alert remains in effect for the entire Chicago area, with another "Air Pollution Action Day" alert declared as wildfire smoke from Canadian wildfires continues to impact parts of the Midwest.

An air quality alert is in effect until midnight Thursday for the Chicago area as Canadian wildfires continue.

Toxic air spreads hundreds or even thousands of miles from where wildfires burn. Last week, Chicago felt the sting—and warnings weren’t enough to protect health.

As of early Thursday, the air quality for much of northeast Illinois, including multiple suburbs to the north and some to the west, fell into the "unhealthy for sensitive groups" category, which ranks as level two on a scale of six.

Canadian wildfires brought some of the worst air quality in the world to Chicago last week. Since then, the AQI has gotten a bit better, but this does beg a couple of questions: How do I keep myself safe during poor air quality days? How does poor air quality affect my health?

For Saturday, look for clouds to increase through the day with highs in the 70s and cooler temperatures along the lake in the 60s.