Cities are hotter: Urban Heat Islands-Temperature Risers
An urban heat island (UHI) is an urban area of metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak. UHI is most noticeable during the summer and winter. The main cause of the urban heat island effect is the dense concentration of pavement, buildings, and other surfaces that absorb and retain heat.