How does the temperature of urban areas like Atlanta, Philadelphia, and Chicago differs from that of surrounding rural areas?

1 Answer
Jan 23, 2018

Warmer then the surrounding


Large cities create what is called an "urban heat island" with warmer temperatures than the surrounding rural environment.

The main reason is that in a city the land surface is modified by the presence of artificial covers (such as paved roads) that generally reduce the albedo (reflective power) of the land thus enhancing the intake of solar radiation.

Moreover the presence of buildings, mostly if tall such as skyscrapers, changes the circulation patterns of the wind within the city. In general wind speed is reduced (with some exceptions in case of the buildings generating venturi effects with local acceleration of the air flow due to narrowing space between the buildings) allowing the heat to be retained.

Finally in the cities a degree of heat is generated as byproduct of energy usage (cars, AC, illumination, heat loss from heated buildings).

The temperature recorded in a large city can be up to 5 Celsius warmer in average than the one of the surrounding rural area.