Extreme heat is the leading weather-related killer in the United States, with heat waves responsible for more deaths than other extreme weather events like tornadoes, flooding, or hurricanes, according to the National Weather Service.
The most serious health impacts of a heat wave are often associated with warm overnight temperatures, the Environmental Protection Agency warns.
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Warmer overnight temperatures are also fueled by urban development. Cities with heat-retaining concrete and asphalt are particularly vulnerable to higher temperatures when vegetation is lost to more paved surfaces and buildings, according to the EPA.
Compared with surrounding rural areas, urban locations have higher overall temperatures, especially at night. This is known as the "urban heat island" effect.
The temperature may even vary greatly between one location and another nearby.
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Cities have been taking action, especially in recent years, to cool down the atmosphere during the summer months with things like water features, shade, reflective surfaces, "cool pavement," or vegetation.
This story was originally published by Leah Sarnoff and Daniel Peck with the Scripps News Group in Phoenix.
