100 Degrees? That May Be Low End of What's Set for West

A punishing heat cap is settling over the western US this weekend, setting the stage for what could be the region's hottest stretch of the year so far. An intense heat dome—explained by the AP as a "phenomenon in which atmospheric conditions trap heat, accentuating and prolonging already high temperatures"—is forecast to drive temperatures 10 to nearly 20 degrees above normal, from Southern California to the northern Rockies and Plains, with roughly 40 million people under heat alerts and dozens of daily records likely to be smashed, per CNN. California's Death Valley could hit 126 degrees Fahrenheit; Phoenix and Tucson in Arizona, Las Vegas, and much of California are expected to reach or soar past 110, while Montana's Billings and Salt Lake City may break August records just weeks after setting all-time highs.

The National Weather Service has placed more than 12 million people under its highest "extreme" heat risk level, warning that anyone without reliable cooling or hydration is vulnerable. Yahoo notes that six states are under extreme-heat warnings on Friday, including California, Arizona, Nevada, Utah, Oklahoma, and western Arkansas. Overnight lows will stay abnormally warm, limiting relief and raising the risk of heat illness, which already kills more Americans each year than hurricanes, tornadoes, and lightning combined. The prolonged dome is also baking already dry land, heightening wildfire danger and straining the drought-stressed Colorado River system, where water levels at Lake Mead and Lake Powell are at historic lows and expected to fall further. NPR has tips on how to stay safe in affected areas.