Urban heat island
An urban heat island is an urban area with a higher local temperature compared to the surrounding rural areas. Heat islands are artificial microclimates caused by human activity (e.g. energy plants, heat exchangers) and land development (dark surfaces that absorb heat, such as roads).
This phenomenon can aggravate heat waves and affect biodiversity, by pushing certain species out of the area and attracting other, more thermophile species.
Sacramento's heat islands. The redder the colour, the higher the temperature. © NASA/Marshall Space Flight Center and Global Hydrology and Climate Center