Wildfire smoke brings hazy skies and poor air quality to Chicago today, with hot and humid weather building into the weekend.

Concern for poor air quality in the greater Chicago area remains as the Illinois EPA extends its alert until Thursday night. The city also is expected to get slightly warmer each day until the weekend.

The hazy skies in the Chicago area are the visible sign of the poor air quality on Thursday as smoke from Canadian wildfires sent Chicago to the top of the list of most polluted cities in the world.