The climate research non-profit known as First Street Foundation, says worsening extreme heat and humidity from climate change will bring extremely dangerous heat indices to much of the country in the next 30 years.
They say the intensity and frequency of the hottest days of the year will also increase.
MORE NEWS | Plummeting to Earth? How space weather is causing satellites to fall from orbit
Plummeting to Earth? How space weather is causing satellites to fall from orbit
That includes a so-called "extreme heat belt," that would stretch from Texas to the Great Lakes.
First Street found more than 100 million Americans in that area will experience temperatures above 125 degrees during their hottest stretches of the year.
Eyewitness News meteorologist Jeff Smith explains more about the study and the extreme heat belt in the video above.
----------
* Get the AccuWeather App
* More AccuWeather
* Follow us on YouTube
* More local news
* Sign up for free newsletters
* Download the abc7NY app for breaking news alerts