Today in our environmental science lecture, we'll discuss the impact of urban green spaces on city temperatures. Recent studies show that parks can reduce surrounding air temperatures by up to 4 degrees Celsius during heatwaves. This cooling effect, however, depends on the park's size and the density of trees. For instance, a large park with dense canopy can create a 'cool island' that extends several hundred meters beyond its borders. In contrast, small gardens with mostly grass have a minimal effect. Interestingly, the presence of water features, like ponds, also enhances cooling but requires careful maintenance to avoid mosquito breeding. So, while green spaces are beneficial, their design is crucial for maximizing temperature reduction.