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Oppressive and dangerous heat will continue to threaten millions of Americans in the United States
According to FOX Weather, 77 million people were under heat alerts to start the weekend.
The midsummer heat is expanding eastward, with new daily record temperatures expected, according to the National Weather Service (NWS).
Heat advisories and warnings are also in effect for other areas of the country.
NASA IMAGES SHOW LAS VEGAS LAKE MEAD WATER LEVELS LOWEST SINCE 2000
Heat indices above 105 degrees Fahrenheit are expected in parts of southern Utah and northern Arizona, with some areas reaching 110 degrees.
Daytime temperatures are expected to eclipse the century mark in the Central Plains, and record high temperatures will extend from that region into the Northeast on Saturday.
Sunday is expected to warm the Northeast even more, while an approaching cold front will chill parts of the Midwest Sunday into Monday.
Although the 2022 New York City Triathlon is still scheduled to go ahead 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.
The heat will continue early next week in the southern Plains and mid-south.
This comes as severe thunderstorm watches are already issued for 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 can also produce flash floods.
HEAT WAVE CAUSES MORE THAN 1,000 DEATHS IN PORTUGAL
The NWS office in Chicago confirmed a tornado touched down in Naperville, Illinois on Saturday morning.
By Sunday, the threat will move inland from the Northeast to the lower Great Lakes.
In the southwest and south of the Rockies, monsoonal moisture will cause locally heavy rain.
Heat waves in the US follow record temperatures in Europe.
Britain broke its record for the highest temperature ever recorded on Tuesday.
The Met Office’s 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, according to the NWS.
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Research supported by the National Heart, Lung, and Blood Institute found that each additional day of extreme summer heat between May and September from 2008 to 2017 was linked to 0.7 additional deaths per 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 additional deaths each year,” the institute said in June.
51.87% of the contiguous United States is currently experiencing moderate to exceptional drought.
Reuters and The Associated Press contributed to this report.
Julia Musto is a reporter for Fox News Digital. You can find her on Twitter at @JuliaElenaMusto.