We are facing a potentially staggering expansion of dangerous heat over the coming decades.

 

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. 

 

The results highlight a stark choice: We can continue on our current path, where we fail to reduce heat-trapping emissions and extreme heat soars. Or we can take bold and rapid action now to reduce emissions and prevent the worst from becoming reality. 

 

Data are drawn from the July 2019 report, Killer Heat in the United States: Climate Choices and the Future of Dangerously Hot Days.

 

Data and fact sheets are also available by Congressional district for every district in the lower 48 states. 

 

Photo: logoboom/Shutterstock