Chicago set a heat index record Thursday after “feels like” temperatures at an airport hit a blistering 120 degrees Fahrenheit, smashing the previous record set in July 1995 during a heat wave that killed more than 500 people in the city.
Heat index values measure what conditions feel like to the human body when humidity and air temperatures are combined. An intense heat wave across the Midwest and through the South sent heat index values skyrocketing well into the triple digits this week, as 98 million people remained under heat alerts Thursday.
Chicago’s previous heat index record of 118 F, set July 13, 1995, stood for nearly three decades. Just before 3 p.m. Thursday, however, a heat index of 120 F was recorded at O’Hare International Airport, becoming the city’s highest in recorded history.
The heat wave is caused by a “heat dome,” or a ridge of high pressure, that stalled over the central U.S., trapping hot air over the region.
Temperatures up to 20 degrees hotter than normal have been recorded from the Upper Midwest to the Gulf Coast, with heat indexes well over 100 F in Missouri, Iowa and Illinois.
Cities across the southern part of the U.S. are also baking. High temperatures Thursday were forecast to hit 105 in Houston, 106 in Dallas and 101 in Memphis, Tennessee.
Temperatures are expected to cool off in the Midwest heading into the weekend, but high heat and humidity will linger across the South into next week.
Studies have shown climate change is making heat waves more likely to occur — and longer and more severe when they do.
This article was originally published on NBCNews.com