Hot Cities Getting Hotter in the US

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Cities are already warmer than the surrounding rural and natural environments, a phenomenon known as an urban heat islands.  Densely packed buildings, impervious streets, sidewalks, and parkings lots, as well as less vegetation all contribute to a daytime accumulation of solar radiation that makes urban areas hotter well past the cooling effects of sundown.

Climate Central has published a new report that took at look at the increases in temperature in sixty of the largest U.S. cities.  The report notes that over 80 percent live in urban areas in the United States and the trend since the 1970s has been towards warmer summers.  Excessive heat is the number one weather related killer of residents in the U.S. and days that reach over 90 degrees Fahrenheit are particularly dangerous because they can be accompanied by higher ozone pollution that can trigger life threatening asthma and heart attacks.

Map showing the urban heat island effect in Cincinnati, Ohio.
Map showing the urban heat island effect in Cincinnati, Ohio.

Of those sixty cities examined, a 57 have measurable urban heat islands.  Las Vegas had a measured one day differential of 27 degrees Fahrenheit compared to its surrounding rural areas.  On average across all 60 cities, urban summer temperatures were 2.4°F higher than surrounding rural areas.

The top ten cities with the most intense urban heat islands:

  • 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)

You can explore the data for all sixty cities in the interactive below.  Access to the full report and summary: Hot and Getting Hotter: Heat Islands Cooking U.S. Cities.

U.S. Urban Heat Islands



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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.