LONDON, UK – Vast swaths of the continental US will be experiencing prolonged and dangerous heatwaves by the middle of the century, with the heat index in some areas above 100F (38C) for weeks on end, according to an alarming new study published on Monday.

Almost two-thirds of Americans, who live in mostly southern and central states, will be at risk from the critical temperature increases, according to a Washington Post analysis of data from the non-profit First Street Foundation, which used current trends to predict the number of extreme heat days 30 years into the future.

“A changing environment means higher temperatures and changing humidity, creating conditions which exacerbate the effects of extreme heat,” the study reports.

Property owners can find out their risk factor using an interactive tool published with the foundation’s report that provides historical and current heat data for each city, county or zip code, and a prediction of the rate of increase for the next three decades, along with its percentage likelihood of a three-day or longer heatwave above 100F.

To read more, click on The Guardian