Oppressive and dangerous heat will continue to threaten millions of Americans across the U.S.
According to FOX Weather, 77 million people were under heat alerts to start the weekend.
Mid-summer heat is expanding eastward, with new daily record high temperatures projected to be set, according to the National Weather Service (NWS).
Heat advisories and warnings are also in effect for other areas of the country.
In parts of southern Utah and northern Arizona, heat indices of over 105 degrees Fahrenheit are anticipated, with some areas extending to a temperature of 110 degrees.
Daytime temperatures are expected to eclipse the century mark in the Central Plains and record-breaking high temperatures will extend from that region to the Northeast on Saturday.
Sunday is slated to grow even hotter in the Northeast, while an approaching cold front will cool down parts of the Midwest from Sunday into Monday.
While the 2022 New York City Triathlon is still scheduled to continue on Sunday, FOX Weather reported that organizers have decided to shorten parts of the event.
The 2022 Boston Triathlon has been moved to next month.
Heat will continue into early next week for the southern Plains and mid-South.
This comes as severe thunderstorm watches are already issued across the upper Midwest and lower Great Lakes.
Parts of the upper Mississippi Valley and Great Lakes are expected to see tornadoes, damaging winds and large hail. Some storms may also produce flash flooding.
The NWS office in Chicago confirmed a tornado touched down in Naperville, Illinois, on Saturday morning.
By Sunday, the threat will impact the interior Northeast to the lower Great Lakes.
In the Southwest and southern Rockies, monsoonal moisture will bring locally heavy rainfall.
Heat wave conditions in the U.S. follow record temperatures in Europe.
Britain surpassed its record for the highest temperature ever registered on Tuesday.
Met Office chief scientist Stephen Belcher said such temperatures in Britain were "virtually impossible" without human-driven climate change.
Thousands of heat-related deaths have been reported in Spain and Portugal.
Heat is the leading cause of weather-related deaths most years, per the NWS.
Research supported by the National Heart, Lung, and Blood institute found that each additional day of extreme summer heat between May to September of the years from 2008 to 2017 was linked to an additional 0.7 deaths for every 100,000 adults.
"In other words, an increase in hot summer days, where it felt at least 90 degrees, was associated with an average of 1,373 extra deaths each year," the institute said in June.
51.87% of the contiguous U.S. is currently experiencing moderate to exceptional drought.
Reuters and The Associated Press contributed to this report.