Heat Island Effect

Cities tend to be warmer than rural locations. This is typically due to the infrastructure built within a city, such as buildings and roads, which absorb heat from the sun and slowly release it during the day and into the night. This is known as the heat island effect. The heat increases local temperatures. Heat Islands can be reduced by installing cool roofs and other surfaces with a high albedo. 

https://www.epa.gov/heatislands/