Today in our environmental science lecture, we'll discuss urban heat islands. Cities tend to be warmer than surrounding rural areas because concrete and asphalt absorb and re-radiate heat. However, trees and green roofs can significantly reduce this effect. A study in Melbourne found that increasing tree cover by 10% could lower daytime temperatures by up to 2.5 degrees Celsius. Interestingly, the cooling effect was strongest in the late afternoon, not at noon as many assume. This is because trees shade surfaces that have been heating all day, and evaporation from leaves peaks later. Therefore, urban planners should prioritize planting trees in residential areas rather than just commercial zones.