Turning up the Heat: Urban Heat Islands in Snohomish County

Exposure to excessive heat kills more people than any other weather related cause in North America, yet the risks are uneven. Accounting for differences in geography, many studies have found urban environments to be more heat-hazardous than adjacent rural areas due to lack of vegetation, urban form, and the cumulative effects of impervious surface. These areas are called Urban Heat Islands. People aged 65 and over are the most at-risk to the hazards of heat exposure, however it has also been found that people of color and those in poverty are often disproportionately represented in areas that experience the greatest heat island effects. Using a cross-sectional case study of Snohomish County, I used land cover and temperature data to determine whether urban heat islands exist in this county. I then used U.S. Census data to determine who lives in these heat islands. Lastly, I examined the American Household Survey to find the percentage of the population who owned an air conditioner; the number one personal preventative measure. My results demonstrate that Snohomish County is similar to other areas of the United States. In this county, areas covered by impervious surface and less vegetation are hotter than adjacent suburban and rural areas, and people of color and those living in poverty are predominately represented in these areas. The highest concentrations of people 65 and over are also living in the urban heat islands. Lastly, I present some policy solutions to mitigate the outcomes of future heat events