Smoky air from Canadian wildfires envelops Chicago for 3rd day. What does this mean for summer?

Tiny, airborne smoke particles blowing in from Canadian wildfires resisted dispersal from a steady, light rain across the Chicago area Wednesday, concentrating even more Thursday to reach levels unhealthy for the general public. The smoke pushed northeast Illinois into its third day in a row of bad air quality Friday and the state into its first two air pollution action days of the year.