Temperatures over 100 degrees and brutally high humidity will combine to deliver a potentially dangerous heat wave to much of the central and southern U.S. this week.
"This may be one of the worst heat waves in the last few decades," the National Weather Service warned.
Some 130 million Americans will endure heat indexes of at least 100 degrees, according to the Weather Channel.
The intense heat will spread into the mid-Atlantic and Northeast by next weekend. Only the Northwest will not feel the full effects of the heat wave.
This will be the hottest weather so far this summer in the central U.S., AccuWeather said. Heat advisories and warnings have been posted in 16 states in the central and southern U.S., the weather service said.
Cities such as Dallas, Chicago, Oklahoma City, Kansas City, St. Louis and Des Moines are all in the zone of extreme heat. Some daily record high temperatures are possible in a few locations, but no all-time records seem likely.
Milwaukee, Chicago, Detroit and Toledo could see 100-degree temperatures on Friday, WeatherBell meteorologist Ryan Maue said.
The heat index — which factors in both temperatures and humidity — could approach 120 degrees in some spots