In 120 degree temperatures, some airplanes might not takeoff. Power grids strain as the outside air keeps transmission lines from cooling.

And for desert dwellers, a cold bottle of water and some shade can mean the difference between life and death. Parts of the U.S. Southwest, long accustomed to triple-digit temperatures, are preparing for a heat wave and, in Phoenix, officials

are warning residents that the mercury may rise to 120, approaching Phoenix’s all-time record of 122. READ MORE