Killer heat in the United States: The future of dangerously hot days
This interactive mapping tool shows the rapid, widespread increases in extreme heat projected to occur across the United States due to climate change. Information is presented by county and includes all 3,109 counties in the contiguous US.
For this national analysis, extreme heat is measured according to the heat index, the combination of temperature and humidity that together create a “feels like” temperature.
Four different heat index thresholds are featured, each of which brings increasingly dangerous health risks: above 90°F, above 100°F, above 105°F, and “off the charts.” (Off-the-charts days are so extreme they exceed the upper limits of the National Weather Service heat index scale, which starts topping out at or above a heat index of 127°F, depending on the combination of temperature and humidity.)
Three time frames are featured—historical, midcentury, and late century—and three different scenarios of climate action are considered.
Data are drawn from the July 2019 report, Killer Heat in the United States: Climate Choices and the Future of Dangerously Hot Days.