Cairo, Istanbul, and Nairobi – each of these three megacities has an official population of up to 16 million, with even more uncounted residents in the swelling settlements on the outskirts of town. Traffic chaos is the norm, and during the summer, the heat in the city is almost unbearable. Climate change will further exacerbate the issues faced by booming urban centers over the next few decades. But how can the microclimate in these areas be improved?