PHOENIX (AP) — The Southwestern U.S. is about to feel the wrath of a punishing heat wave that includes a forecast of 120 degrees in Phoenix — a temperature not seen in the desert city in more than 20 years.
The broiling temperatures will also be felt in Las Vegas and Southern California, creating a public health hazard. Rising temps are being closely watched by everyone from airline pilots and emergency room doctors to power grid managers and mountain cities unaccustomed to heat waves.
Even cities accustomed to dealing with 110-degree days are grappling with the new problems that arise from 120 degrees.
Here is a few things to know about the heat wave:
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HITTING 120 IS RARE
The heat wave, which is expected to peak Tuesday, is forecast to be the hottest weather in Phoenix in decades.
Wunderground Weather Historian Christopher C. Burt said Phoenix temperatures rose to 120 degrees and above only three times in recorded history — twice in 1990 and once in 1995.
Burt said the city has hit 118 degrees 11 times, most recently last summer.
It could be worse: Death Valley could see 124 degrees on Tuesday.
AIRLINES WATCHING THE HEAT
When the temperature soars, it’s harder for airplanes to take off.
American Airlines pilot Shane Coffey said extreme heat creates changes in the air density that make it harder for airplanes to take off, meaning pilots have to use more thrust or impose weight restrictions such as flying with less cargo.
Air density on a 90-degree day in Denver at more than 5,000 feet elevation is similar to a 120-degree day in Phoenix at 1,100 feet above sea level, he said.
In 1990, amid a similar heat wave, flights were cancelled at the Phoenix airport because there was too much uncertainty about how the heat would affect aviation performance. Now, airlines have a better understanding, but the heat is still a…