Ever notice how downtown is warmer than a park on hot summer day? That’s the heat island effect. Heat reflects off of concrete, buildings, pavement, and streets causing the immediate air temperature to rise as much as ten degrees.
Trees, shrubs, vines, grasses, and ground cover plants shade surfaces and evapotranspire (water emitted from leaves is evaporated). These processes cool the surrounding air. Hence, the cooling effect of a park or greenspace.