Urban green roofs can help cool cities and reduce flooding. A study measured heat and water fluxes on a large green roof in France. They used special instruments to measure how much heat and water were moving in and out of the roof. On sunny days, heat measurements followed sunlight, but on cloudy days, they changed a lot. Wind affected heat movement, and the roof didn't conduct heat well when dry. The amount of water evaporating was overestimated, likely due to measurement uncertainties. Overall, the study shows how green roofs affect heat and water in cities.