Tens of millions of Americans will be under heat warnings, watches and advisories as temperatures reach above 100 degrees Fahrenheit (37 Celsius) in major cities such as Chicago, New York and Philadelphia, the National Weather Service said.
"The combination of hot temperatures and high humidity will combine to create a dangerous situation in which heat illnesses are likely," the service said in a warning for Chicago, the third-largest city in the United States.
The hot weather is especially dangerous for young children, elderly people and people with health problems, it said.
Cities across the region, from the Mississippi River to the East Coast, have set up cooling centers to keep people out of the dangerous heat.
Philadelphia officials warned residents on Twitter not to use fire hydrants, but to go to the city's more than 70 spraygrounds and pools to cool off.
The hot weather had already forced the cancellation of Fourth of July firework shows in several Ohio cities along with a basketball event in Toledo, Ohio, and a concert held by a school district in Minnesota.
During the hottest hours on Saturday, tens of thousands of people are expected to attend hundreds of "families belong together" rallies in cities across the country to protest President Donald Trump's controversial immigration policy.
In addition to the heat wave, the National Weather Service warned communities in drought-stricken parts of Colorado and northern California of prime wildfire weather as hot, arid and windy conditions will persist over the weekend.
Oh, of course. That had to be wedged in there somewhere in a weather report, didn't it?
Fucking yahoo.