Heat wave creates health hazard in southwestern US

The southwestern US is about to feel the wrath of a punishing heat wave that includes a forecast of 120 degrees (48.8 Celsius) 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 (43- Celsius) days are grappling with the new problems that arise from 120 degrees (48.8 Celsius).

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 (32-Celsius) day in Denver at more than 5,000 feet elevation is similar to a 120-degree (48.9-Celsius) 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 concern primarily for smaller, regional jets. Airlines will be closely monitoring the heat this week and some flights could be affected.