Itxayana Ceballos is sprayed with water as she keeps cool at Tempe Beach Park, as the temperature climbs to 116 degrees Fahrenheit (46.7 degrees Celsius) in Tempe, Arizona.
An "atmospheric blast furnace" engulfed the sunbaked U.S. West in dangerous triple-digit temperatures on Friday, forecasters said, raising concerns for homeless people and others unable to escape near record temperatures expected over the weekend.
An excessive heat warning is in effect for the sun-baked deserts of southeast California, parts of Nevada and southern Arizona through Sunday, as a large area of high pressure traps hot air across the area, the National Weather Service said.
Highs of 129 F (54 C) are forecast for California's Death Valley over the weekend, while the tourist mecca of Las Vegas is expected to match all-time record highs of 117 degrees (47 C) Saturday through Monday.
"An atmospheric blast furnace will be at full throttle heading into the weekend over the interior West with heat reaching dangerous levels," said AccuWeather.com senior meteorologist Alex Sosnowski.
"While many folks over the interior West are accustomed to and expect hot weather during the summer, the developing pattern will take the heat to the extreme," he added.
The National Weather Service warned that the "exceedingly high temperatures" can cause potentially fatal heat stroke, and noted that those without air conditioning or working outdoors were particularly at risk.
In an effort to safeguard hundreds of homeless people in Phoenix, where temperatures are expected to top 118 F (48 C) over the weekend, emergency shelters are temporarily laying on an extra 150 beds.
"Phoenix is a major city with a lot of concrete that tends to hold a lot of that heat in, so it's just like you're in a dry sauna," said Irene Agustin, of the Central Arizona Shelter Services nonprofit in Phoenix.
"When you're homeless ... you are out in the elements for long periods of time ... it can cause heat exhaustion, illness and sometimes death," she added.
The National Weather Service said the heat warning currently remains in place through Sunday, but could be extended into next week should conditions persist.