English: Figure 2  The urban heat island (UHI) in several geographical situations: inland city (the most studied), coastal cities, cities in mountainous areas, and polar cities in wintertime. During daytime, in inland cities, suburban areas are often slightly warmer than their countryside, especially industrial and commercial areas with large car parks. Although coastal cities are generally cooler than inland cities nearby, they can during the day be warmer than their immediate countryside, because of the blocking of the sea breeze by buildings. During nighttime, when meteorological conditions are calm, city centers are generally warmer than the countryside with strong UHI. Cities in valleys can be an exception due to orographic flows. The presence of hills can also modulate the intensity of the nocturnal UHI, especially during clear and cold nights.