There are certain truths that accompany summer in Phoenix: high-30s temperatures persist well past sundown. It’s not considered abnormal to drive with oven mitts or ice packs in the car. And after a certain threshold, even the “it’s a dry heat” jokes cease being funny.

Usually, the hot season is met with a certain amount of pearl-clutching disbelief by people outside of Arizona. Meanwhile, locals shrug, knowing simply to stay indoors as much as possible or escape to the cooler climes of northern Arizona.

But this week has felt different, even for seasoned desert-dwellers. The U.S. Southwest is experiencing its worst heat wave in decades. Excessive heat warnings have been in effect from Arizona to California and will be for the remainder of the week.

How hot has it been? On Monday, temperatures in Phoenix hit 48 C, according to the National Weather Service, which announced the record-tying heat against a stock image of a flaming ball of fire.

It’s been so hot that even veteran local meteorologists are appending their tweets with #makeitstop.

And it was so hot that at least 50 flights have been cancelled this week at Phoenix Sky Harbor International Airport.

American Airlines alerted its customers over the weekend, offering fee-free changes to upcoming flights that were departing or arriving at Phoenix between 3 and 6 p.m., when temperatures peak.

The Fort Worth-based airline cancelled 50 flights Monday in and out of Phoenix and expected delays for at least seven flights to Sky Harbor on Tuesday, according to American Airlines spokesman Ross Feinstein.

Flights on American Eagle, American Airlines’ regional brand, were the most affected, because they use Bombardier CRJ planes that can only operate at temperatures of 48 C or below, Feinstein said. Flights on larger Airbus and Boeing planes were not cancelled because they are able to operate at higher maximum temperatures: 53 C for Airbus and 52 C for Boeing.

Each aircraft manufacturer sets its own parameters for operating temperatures, Feinstein said. As of Tuesday morning, Sky Harbor officials said no other airlines had been affected.

The heat shows no sign of relenting soon.

The National Weather Service broke out the magenta — a colour category little known to the rest of the U.S. — to illustrate parts of Arizona that would be under “rare, dangerous, and very possibly deadly” heat for the rest of the week.

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The record for Phoenix was set June 26, 1990, when temperatures reached 50 C. Flights out of Sky Harbor that day were grounded, too.

Only three times in recorded history has the temperature hit 49 C or above: twice in 1990 and once in 1995, National Weather Service meteorologist Chris Kuhlman told the Washington Post.

Historically, average temperatures for Phoenix this time of year have remained between 40 and 43 C, he said.

Kuhlman, who is based in Phoenix, admitted that he woke up at 4 a.m. Tuesday to do yard work before the sun came up.

Even at that hour, it was 32 C outside.

“Normally, it’s hot but it’s not intolerable. You get acclimated to your surroundings. You kind of get used to the heat,” Kuhlman said. “But when it’s even this far above what the normal is, even for us that live here ... it’s dangerous to be doing stuff outside. Anything, I suppose.”

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