The heat index in the Chicago area this week will soar above 100 degrees, and the places most impacted by the heat could share a notable characteristic. The effects of extreme heat highlight disparities across Chicago neighborhood in more ways than one, according to recent studies. Areas with a healthy tree canopy can feel up to 10 degrees cooler than nearby areas without trees, experts say, and neighborhoods with lacking tree coverage tend to be under-resourced areas, that data has shown.