Summer in the City: Hot and Getting Hotter

In this report from Climate Central, the combined impacts of climate change and urban heat islands are described, as taken from analysis of 60 of the biggest cities across the U.S. The study looked at how much hotter the urban environments are compared to nearby rural areas, and how these temperature differences have been changing since 1970.

The website provides an interactive visual interface to view graphic data of temperature and related air pollution by city. The full length report is informative and concise while also visually engaging for the general public.    

Climate Central explains that cities are almost always hotter than the surrounding rural area but global warming takes that heat and makes it worse. In two thirds of the cities analyzed (41 of 60), urbanization and climate change appear to be combining to increase summer heat faster than climate change alone is raising regional temperatures. In three quarters (45 of 60) of cities examined, urbanized areas are warming faster than adjacent rural locations. In the future, this combination of urbanization and climate change could raise urban temperatures to levels that threaten human health, strain energy resources, and compromise economic productivity.

The top 10 cities with the most intense summer urban heat islands (average daily urban-rural temperature differences) over the past 10 years are:

• Las Vegas (7.3°F)
• Albuquerque (5.9°F)
• Denver (4.9°F)
• Portland (4.8°F)
• Louisville (4.8°F)
• Washington, D.C. (4.7°F)
• Kansas City (4.6°F)
• Columbus (4.4°F)
• Minneapolis (4.3°F)
• Seattle (4.1°F)

Higher urban summer temperatures pose serious health risks from exposure to high levels of ground-level ozone (which is explored in Section 4 of the report), as well as from heat stress, heat stroke, and higher risks of heart and lung problems. Hotter urban summers can also lead to increased energy demands as more people turn to air conditioners for relief. These higher energy demands have the potential to stress the current electricity grid, particularly at peak electricity times.


Climate Central surveys and conducts scientific research on climate change and informs the public of key findings. Their scientists publish and journalists report on climate science, energy, sea level rise, wildfires, drought, and related topics. Climate Central is a non-profit, is not an advocacy organization, and does not lobby or support any specific legislation, policy or bill.


Publication Date: August 20, 2014

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