More than 60 million in US experiencing temperatures over 100 degrees
Excessive heat watches and warnings are effective in nine states.
Tens of millions of residents in the Southwestern U.S. are experiencing dangerous heat, with triple-digit temperatures blanketing much of the region.
The most brutal heat is concentrated over Texas, where recording-breaking temperatures are expected in Amarillo, Abilene and possibly Dallas, near 105 degrees.
In California, Furnace Creek is expected to hit 118 degrees, while Phoenix is predicted to be 113 degrees, and Las Vegas 109 degrees.
While the heat is expected to ease in the coming days across the Southwest, fire danger in the region will ramp up as strong, gusty winds replace the blistering temperatures.
Red flag warnings will begin on Sunday from southern Nevada to northern New Mexico. Fire watches have also been issued for portions of Arizona, New Mexico and Colorado.
More than 85% of the West is experiencing drought conditions, making the fire danger even more of a threat.
The scorching heat will then move east, with the brunt of it focused over the center of the country on Monday. Widespread hot air temperatures and humid conditions will produce triple-digit heat index values across much of the Plains and into the South Monday afternoon. It will be feeling like it's 105 to 110 degrees in some cities from Texas and into the Plains as far north as Nebraska and Southern states like Alabama and Tennessee during the peak heat on Monday.
On Tuesday, widespread temperatures in the 90s in the Midwest and much of the Southeast. Daily record highs will likely be challenged from Michigan to North and South Carolina by midweek.
ABC News' Daniel Amarante and Dan Peck contributed to this report.