Climate crisisSouthwest to Endure 50 Days or More a Year When Temperature “Feels Like” Exceeding 105 Degrees

Published 16 July 2019

Increases in potentially lethal heat driven by climate change will affect every state in the contiguous U.S. in the decades ahead. Few places would be unaffected by extreme heat conditions by midcentury and only a few mountainous regions would remain extreme heat refuges by the century’s end. The dangerously soaring heat across the U.S. is posing unprecedented health risks.

Increases in potentially lethal heat driven by climate change will affect every state in the contiguous U.S. in the decades ahead, according to a new report and accompanying peer-reviewed study in Environmental Research Communications, both by the Union of Concerned Scientists, released today. Few places would be unaffected by extreme heat conditions by midcentury and only a few mountainous regions would remain extreme heat refuges by the century’s end.

Without global action to reduce heat-trapping emissions, the number of days per year when the heat index—or “feels like” temperature—exceeds 100 degrees Fahrenheit would more than double from historical levels to an average of 36 across the country by midcentury and increase four-fold to an average of 54 by late century. The average number of days per year nationwide with a heat index above 105 degrees Fahrenheit would more than quadruple to 24 by midcentury and increase eight-fold to 40 by late century.

UCS says that the analysis, titled “Killer Heat in the United States: Climate Choices and the Future of Dangerously Hot Days” shows a hotter future that’s hard to imagine today. Nearly everywhere, people will experience more days of dangerous heat even in the next few decades. By the end of the century, with no action to reduce global emissions, parts of Florida and Texas would experience the equivalent of at least five months per year on average when the “feels like” temperature exceeds 100 degrees Fahrenheit, with most of these days even surpassing 105 degrees. On some days, conditions would be so extreme that they exceed the upper limit of the National Weather Service heat-index scale and a heat index would be incalculable. Such “off-the-charts” conditions could pose unprecedented health risks.