Climate change is making cities hotter. This has negative effects on health and well being for billions of people around the world. In Baltimore, the city is combatting the urban heat island effect by replacing darkly colored, flat roofs with lightly colored reflective cool roofs. A team of Johns Hopkins investigators is studying how these cool roofs can help city residents adapt to climate change, improve their indoor air quality, and sleep and breathe easier. This simple solution may be key to reducing the urban heat island and creating a cooler, more equitable city.