Why it's hotter in the city

Published On: Jun 15 2012 09:45:50 AM CDT   Updated On: Jun 15 2012 10:20:15 AM CDT

Why does your car thermometer in the city read 105 degrees while the actual high is only 92? Blame the urban heat island effect.

On a hot, sunny summer day, roof and pavement surface temperatures can be 50 to 90°F hotter than the air, while shaded or moist surfaces -- often in more rural surroundings -- remain close to air temperatures. These surface urban heat islands, particularly during the summer, have multiple impacts and contribute to atmospheric urban heat islands. Air temperatures in cities, particularly after sunset, can be as much as 22°F warmer than the air in neighboring, less-developed regions.

Elevated temperatures from urban heat islands, particularly during the summer, can affect a community’s environment and quality of life. While some impacts may be beneficial, such as lengthening the plant-growing season, the majority of them are negative. These impacts include:
increased energy consumption
elevated emissions of air pollutants and greenhouse gases
compromised human health and comfort
impaired water quality.