Urban development leads to fewer shaded areas and more heat-absorbing paved surfaces. Cities tend to be warmer than their rural surroundings as a result, a phenomenon known as the urban heat island (UHI) effect. During the summer daytime, cities can be up to 12℃ hotter than rural areas.
UHIs are a major environmental hazard for urban dwellers. Research suggests that for each 1℃ rise in temperature, the risk of death increases by between 1% and 3%. Heat exposure also increases the risk of suffering cardiovascular and respiratory illnesses.
